Wireless communication method and wireless communication terminal for coexistence with legacy wireless communication terminal

ABSTRACT

A wireless communication terminal for wireless communication is disclosed. The wireless communication terminal includes: a transceiver; and a processor. The processor is configured to transmit a non-legacy physical layer frame including a legacy signaling field including information decodable by a legacy wireless communication terminal by using the transceiver.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/KR2016/006976 filed on Jun. 29, 2016, which claims the priorityto Korean Patent Application No. 10-2015-0092525 filed in the KoreanIntellectual Property Office on Jun. 29, 2015, and Korean PatentApplication No. 10-2015-0117434 filed in the Korean IntellectualProperty Office on Aug. 20, 2015, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an efficient wireless communicationmethod in a wireless communication environment in which a legacywireless communication terminal and a non-legacy wireless communicationterminal coexist, and a wireless communication terminal using the same.

BACKGROUND ART

In recent years, with supply expansion of mobile apparatuses, a wirelesscommunication technology that can provide a rapid wireless Internetservice to the mobile apparatuses has been significantly spotlighted.The wireless communication technology allows mobile apparatusesincluding a smart phone, a smart pad, a laptop computer, a portablemultimedia player, an embedded apparatus, and the like to wirelesslyaccess the Internet in home or a company or a specific service providingarea.

One of most famous wireless communication technology is wireless LANtechnology. Institute of Electrical and Electronics Engineers (IEEE)802.11 has commercialized or developed various technological standardssince an initial wireless LAN technology is supported using frequenciesof 2.4 GHz. First, the IEEE 802.11b supports a communication speed of amaximum of 11 Mbps while using frequencies of a 2.4 GHz band. IEEE802.11a which is commercialized after the IEEE 802.11b uses frequenciesof not the 2.4 GHz band but a 5 GHz band to reduce an influence byinterference as compared with the frequencies of the 2.4 GHz band whichare significantly congested and improves the communication speed up to amaximum of 54 Mbps by using an Orthogonal Frequency DivisionMultiplexing (OFDM) technology. However, the IEEE 802.11a has adisadvantage in that a communication distance is shorter than the IEEE802.11b. In addition, IEEE 802.11g uses the frequencies of the 2.4 GHzband similarly to the IEEE 802.11b to implement the communication speedof a maximum of 54 Mbps and satisfies backward compatibility tosignificantly come into the spotlight and further, is superior to theIEEE 802.11a in terms of the communication distance.

Moreover, as a technology standard established to overcome a limitationof the communication speed which is pointed out as a weak point in awireless LAN, IEEE 802.11n has been provided. The IEEE 802.11n aims atincreasing the speed and reliability of a network and extending anoperating distance of a wireless network. In more detail, the IEEE802.11n supports a high throughput (HT) in which a data processing speedis a maximum of 540 Mbps or more and further, is based on a multipleinputs and multiple outputs (MIMO) technology in which multiple antennasare used at both sides of a transmitting unit and a receiving unit inorder to minimize a transmission error and optimize a data speed.Further, the standard can use a coding scheme that transmits multiplecopies which overlap with each other in order to increase datareliability.

As the supply of the wireless LAN is activated and further, applicationsusing the wireless LAN are diversified, the need for new wireless LANsystems for supporting a higher throughput (very high throughput (VHT))than the data processing speed supported by the IEEE 802.11n has comeinto the spotlight. Among them, IEEE 802.11ac supports a wide bandwidth(80 to 160 MHz) in the 5 GHz frequencies. The IEEE 802.11ac standard isdefined only in the 5 GHz band, but initial 11ac chipsets will supporteven operations in the 2.4 GHz band for the backward compatibility withthe existing 2.4 GHz band products. Theoretically, according to thestandard, wireless LAN speeds of multiple stations are enabled up to aminimum of 1 Gbps and a maximum single link speed is enabled up to aminimum of 500 Mbps. This is achieved by extending concepts of awireless interface accepted by 802.11n, such as a wider wirelessfrequency bandwidth (a maximum of 160 MHz), more MIMO spatial streams (amaximum of 8), multi-user MIMO, and high-density modulation (a maximumof 256 QAM). Further, as a scheme that transmits data by using a 60 GHzband instead of the existing 2.4 GHz/5 GHz, IEEE 802.11ad has beenprovided. The IEEE 802.11ad is a transmission standard that provides aspeed of a maximum of 7 Gbps by using a beamforming technology and issuitable for high bit rate moving picture streaming such as massive dataor non-compression HD video. However, since it is difficult for the 60GHz frequency band to pass through an obstacle, it is disadvantageous inthat the 60 GHz frequency band can be used only among devices in ashort-distance space.

Meanwhile, in recent years, as next-generation wireless communicationtechnology standards after the 802.11ac and 802.11ad, discussion forproviding a high-efficiency and high-performance wireless communicationtechnology in a high-density environment is continuously performed. Thatis, in a next-generation wireless communication technology environment,communication having high frequency efficiency needs to be providedindoors/outdoors under the presence of high-density terminals and baseterminals and various technologies for implementing the communicationare required.

Especially, as the number of devices using a wireless communicationtechnology increases, it is necessary to efficiently use a predeterminedchannel. Therefore, required is a technology capable of efficientlyusing bandwidths by simultaneously transmitting data between a pluralityof terminals and base terminals.

DISCLOSURE Technical Problem

An embodiment of the present invention is to provide an efficientwireless communication method and wireless communication terminal.

In particular, an embodiment of the present invention is to provide awireless communication method and a wireless communication terminal forcoexistence with a legacy wireless communication terminal.

Technical Solution

According to an embodiment of the present invention, a wirelesscommunication terminal that communicates wirelessly includes: atransceiver; and a processor. The processor may be configured to receivea non-legacy physical layer frame by using the transceiver and obtains alegacy signaling field including information decodable by a legacywireless communication terminal from the non-legacy physical layerframe, obtain length information indicating information on a duration ofthe non-legacy physical layer frame, from the legacy signaling field,obtain information other than information on the duration of thenon-legacy physical layer frame through a remaining value obtained bydividing the length information by a data size transmittable by a symbolof a legacy physical layer frame, wherein the data size transmittable bya symbol of the legacy physical layer frame is 3 octets when a data rateof the legacy physical layer frame is 6 Mbps, and determine the numberof symbols of data of the non-legacy physical layer frame according to afollowing equation,

$N_{SYM} = {\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{{HE}\;\_\;{PREAMBLE}}} \right)/T_{SYM}} \right\rfloor - b_{{PE}\;\_\;{Disambiguity}}}$

where └x┘ denotes a largest integer less than or equal to x,

L_LENGTH denotes the length information,

m denotes a value obtained by subtracting the remaining value from thedata size transmittable by a symbol of the legacy physical layer frame,

b_(PE) _(_) _(Disambiguity) denotes a value of PE Disambiguity field,

T_(HE PREAMBLE) denotes a duration of non-legacy preamble of thenon-legacy physical layer frame,

T_(SYM) denotes a duration of a symbol of the data of the non-legacyphysical layer frame. The PE Disambiguity field may be set based on theduration of a symbol of the data of the non-legacy physical layer frameand an increment of duration to set a value of the length informationbased on a duration of a symbol of the legacy physical layer frame.

The processor may be configured to obtain a duration of a packetextension which is a padding of the non-legacy physical layer frame,according to a following equation,

$T_{PE} = {\left\lfloor \frac{\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{{HE}\;\_\;{PREAMBLE}}} \right) - {N_{SYM} \times T_{SYM}}}{4} \right\rfloor \times 4}$

where └x┘ denotes a largest integer less than or equal to x,

L_LENGTH denotes the length information,

m denotes the value obtained by subtracting the remaining value from thedata size transmittable by a symbol of the legacy physical layer frame,

T_(HE) _(_) _(PREAMBLE) denotes the duration of non-legacy preamble ofthe non-legacy physical layer frame,

T_(SYM) denotes the duration of a symbol of the data of the non-legacyphysical layer frame.

The increment of duration may be a value obtained by multiplying adifference between a value obtained by performing a ceiling operation ona value obtained by dividing the duration of the non-legacy physicallayer frame after the legacy signaling field by the duration of a symbolof the legacy physical layer frame and the value obtained by dividingthe duration of the non-legacy physical layer frame after the legacysignaling field by the duration of a symbol of the legacy physical layerframe by the duration of a symbol of the legacy physical layer frame.

The processor may be configured to determine a format of a non-legacysignaling field included in the non-legacy physical layer frame based onthe length information.

The processor may be configured to determine the non-legacy physicallayer frame comprises a predetermined signaling field based on thelength information.

The processor may be configured to obtain the information other than theinformation on the duration of the non-legacy physical layer frame basedon the remaining value and a modulation method of a third symbol afterthe legacy signaling field.

The modulation method may be Binary Phase Shift Keying (BPSK) orQuadrature Binary Phase Shift Keying (QBPSK).

According to an embodiment of the present invention, an operation methodof a wireless communication terminal that communicates wirelessly, themethod includes: receiving a non-legacy physical layer frame by usingthe transceiver and obtains a legacy signaling field includinginformation decodable by a legacy wireless communication terminal fromthe non-legacy physical layer frame, obtaining length informationindicating information on a duration of the non-legacy physical layerframe after a legacy signaling field, from the legacy signaling field,obtaining information other than the information on the duration of thenon-legacy physical layer frame through a remaining value obtained bydividing the length information by a data size transmittable by a symbolof a legacy physical layer frame, wherein the data size transmittable bya symbol of the legacy physical layer frame is 3 octets when a data rateof the legacy physical layer frame is 6 Mbps, and determining the numberof symbols of the data of the non-legacy physical layer frame accordingto a following equation,

$N_{SYM} = {\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{{HE}\;\_\;{PREAMBLE}}} \right)/T_{SYM}} \right\rfloor - b_{{PE}\;\_\;{Disambiguity}}}$

where [x] denotes a largest integer less than or equal to x,

L_LENGTH denotes the length information,

m denotes a value obtained by subtracting the remaining value from thedata size transmittable by a symbol of the legacy physical layer frame,

b_(PE Disambiguity) denotes a value of PE Disambiguity field,

T_(HE) _(_) _(PREAMBLE) denotes a duration of non-legacy preamble of thenon-legacy physical layer frame,

T_(SYM) denotes a duration of a symbol of the data of the non-legacyphysical layer frame.

The PE Disambiguity field may be set based on the duration of a symbolof the data of the non-legacy physical layer frame and an increment ofduration to set a value of the length information based on a duration ofa symbol of legacy physical layer frame.

The method may further include obtaining a duration of a packetextension which is a padding of the non-legacy physical layer frame,according to a following equation,

$T_{PE} = {\left\lfloor \frac{\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{{HE}\;\_\;{PREAMBLE}}} \right) - {N_{SYM} \times T_{SYM}}}{4} \right\rfloor \times 4}$

where [x] denotes a largest integer less than or equal to x,

L_LENGTH denotes the length information,

m denotes the value obtained by subtracting the remaining value from thedata size transmittable by a symbol of the legacy physical layer frame,

T_(HE) _(_) _(PREAMBLE) denotes the duration of non-legacy preamble ofthe non-legacy physical layer frame,

T_(SYM) denotes the duration of a symbol of the data of the non-legacyphysical layer frame.

The increment of duration may be a value obtained by multiplying adifference between a value obtained by performing a ceiling operation ona value obtained by dividing the duration of the non-legacy physicallayer frame after the legacy signaling field by the duration of a symbolof the legacy physical layer frame and the value obtained by dividingthe duration of the non-legacy physical layer frame after the legacysignaling field by the duration of a symbol of the legacy physical layerframe by the duration of a symbol of the legacy physical layer frame.

The method may further include determining a format of a non-legacysignaling field included in the non-legacy physical layer frame based onthe length information.

The determining the format of a non-legacy signaling field included inthe non-legacy physical layer frame may include determining thenon-legacy physical layer frame comprises a predetermined signalingfield based on the length information.

The obtaining the information other than the information on the durationof the non-legacy physical layer frame may include obtaining theinformation other than the information on the duration of the non-legacyphysical layer frame based on the remaining value and a modulationmethod of a third symbol after the legacy signaling field.

The modulation method may be Binary Phase Shift Keying (BPSK) orQuadrature Binary Phase Shift Keying (QBPSK).

Advantageous Effects

An embodiment of the present invention is to provide an efficientwireless communication method and wireless communication terminal.

Especially, an embodiment of the present invention provides an efficientwireless communication method and wireless communication terminal in awireless communication environment in which a legacy wirelesscommunication terminal and a non-legacy wireless communication terminalcoexist.

DESCRIPTION OF DRAWINGS

FIG. 1 is a view illustrating a wireless LAN system according to anembodiment of the present invention.

FIG. 2 is a view illustrating a wireless LAN system according to anotherembodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of a stationaccording to an embodiment of the inventive concept.

FIG. 4 is a block diagram illustrating a configuration of an accesspoint according to an embodiment of the present invention.

FIG. 5 is a view illustrating a process that a station sets an accesspoint and a link according to an embodiment of the present invention.

FIG. 6 shows a structure of an IEEE 802.11ac physical layer framesupporting a legacy wireless LAN mode.

FIG. 7 shows a preamble structure of IEEE 802.11n, 11a and 11ac physicallayer frames.

FIG. 8 shows a symbol specific modulation technique of L-SIG, HT-SIG,and VHT-SIG-A for auto detection between 802.11a/n/ac physical layerframes.

FIG. 9 shows a structure of an IEEE 802.11ax physical layer frameaccording to an embodiment of the present invention.

FIG. 10 shows the structures of a legacy physical layer frame and anon-legacy physical layer frame according to an embodiment of thepresent invention.

FIGS. 11 and 12 show structures of a preamble of a non-legacy physicallayer frame according to an embodiment of the present invention.

FIG. 13 shows a structure of a preamble of a non-legacy physical layerframe including a repeated L-SIG according to an embodiment of thepresent invention.

FIG. 14 shows an operation of auto-detecting a non-legacy physical layerframe including a repeated L-SIG by a wireless communication terminalaccording to an embodiment of the present invention.

FIG. 15 shows that a non-legacy physical layer frame signals the formatof a non-legacy physical layer frame according to an embodiment of thepresent invention.

FIG. 16 shows data sub-carriers and pilot sub-carriers of L-SIGaccording to an embodiment of the present invention.

FIG. 17 shows an RL-SIG signaling information through a signalcharacteristic of a frequency region divided into a plurality ofsections according to an embodiment of the present invention.

FIG. 18 shows an operation of detecting RL-SIG by a wirelesscommunication terminal according to an embodiment of the presentinvention.

FIG. 19 shows an RL-SIG signaling information through a signalcharacteristic of a time region divided into a plurality of sectionsaccording to an embodiment of the present invention.

FIG. 20 shows an RL-SIG for transmitting information through a differentmodulation method different than L-SIG according to an embodiment of thepresent invention.

FIG. 21 shows an RL-SIG generated by adding a subcarrier to an L-SIGaccording to an embodiment of the present invention.

FIG. 22 shows that RL-SIG signals information through a pilot subcarrieraccording to an embodiment of the present invention.

FIG. 23 shows an equation for obtaining a transmission time of anon-legacy physical layer frame by a wireless communication terminalaccording to an embodiment of the present invention.

FIG. 24 shows an equation for obtaining length information included inL-SIG by a wireless communication terminal according to an embodiment ofthe present invention.

FIG. 25 shows a method of a wireless communication terminal to determinewhether the existence of a packet extension is unclear according to anembodiment of the present invention.

FIG. 26 shows a method of determining the length of a packet extensionby a wireless communication terminal according to an embodiment of thepresent invention.

FIG. 27 shows that a legacy wireless communication terminal obtains theduration of a non-legacy physical layer frame based on L_LENGTHaccording to an embodiment of the present invention.

FIG. 28 shows that a wireless communication terminal according to anembodiment of the present invention adds a predetermined integeraccording to the format of a non-legacy signaling field while settingL_LENGTH.

FIG. 29 shows a method for determining the length of a packet extensionby a wireless communication terminal according to an embodiment of thepresent invention when adding a predetermined integer according to theformat of a non-legacy signaling field while setting L_LENGTH.

FIG. 30 shows that a wireless communication terminal according to anembodiment of the present invention subtracts a predetermined integeraccording to the format of a non-legacy signaling field while settingL_LENGTH.

FIG. 31 shows a method for determining the length of a packet extensionby a wireless communication terminal according to an embodiment of thepresent invention when adding a predetermined integer according to theformat of a non-legacy signaling field while setting L_LENGTH.

FIG. 32 shows an operation of transmitting a non-legacy physical layerframe and receiving a non-legacy physical layer frame by a wirelesscommunication terminal according to an embodiment of the presentinvention.

MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described belowin more detail with reference to the accompanying drawings. The presentinvention may, however, be embodied in different forms and should not beconstructed as limited to the embodiments set forth herein. Parts notrelating to description are omitted in the drawings in order to clearlydescribe the present invention and like reference numerals refer to likeelements throughout.

Furthermore, when it is described that one comprises (or includes orhas) some elements, it should be understood that it may comprise (orinclude or has) only those elements, or it may comprise (or include orhave) other elements as well as those elements if there is no specificlimitation.

This application claims priority to and the benefit of Korean PatentApplication Nos. 10-2015-0092525, and Nos. 10-2105-0117434 filed in theKorean Intellectual Property Office and the embodiments and mentioneditems described in the respective applications are included in theDetailed Description of the present application.

FIG. 1 is a diagram illustrating a wireless communication systemaccording to an embodiment of the present invention. For convenience ofdescription, an embodiment of the present invention is described throughthe wireless LAN system. The wireless LAN system includes one or morebasic service sets (BSS) and the BSS represents a set of apparatuseswhich are successfully synchronized with each other to communicate witheach other. In general, the BSS may be classified into an infrastructureBSS and an independent BSS (IBSS) and FIG. 1 illustrates theinfrastructure BSS between them.

As illustrated in FIG. 1, the infrastructure BSS (BSS1 and BSS2)includes one or more stations STA1, STA2, STA3, STA4, and STA5, accesspoints PCP/AP-1 and PCP/AP-2 which are stations providing a distributionservice, and a distribution system (DS) connecting the multiple accesspoints PCP/AP-1 and PCP/AP-2.

The station (STA) is a predetermined device including medium accesscontrol (MAC) following a regulation of an IEEE 802.11 standard and aphysical layer interface for a wireless medium, and includes both anon-access point (non-AP) station and an access point (AP) in a broadsense. Further, in the present specification, a term ‘terminal’ may beused to refer to a concept including a wireless LAN communication devicesuch as non-AP STA, or an AP, or both terms. A station for wirelesscommunication includes a processor and a transceiver and according tothe embodiment, may further include a user interface unit and a displayunit. The processor may generate a frame to be transmitted through awireless network or process a frame received through the wirelessnetwork and besides, perform various processing for controlling thestation. In addition, the transceiver is functionally connected with theprocessor and transmits and receives frames through the wireless networkfor the station.

The access point (AP) is an entity that provides access to thedistribution system (DS) via wireless medium for the station associatedtherewith. In the infrastructure BSS, communication among non-APstations is, in principle, performed via the AP, but when a direct linkis configured, direct communication is enabled even among the non-APstations. Meanwhile, in the present invention, the AP is used as aconcept including a personal BSS coordination point (PCP) and mayinclude concepts including a centralized controller, a base station(BS), a node-B, a base transceiver system (BTS), and a site controllerin a broad sense.

A plurality of infrastructure BSSs may be connected with each otherthrough the distribution system (DS). In this case, a plurality of BSSsconnected through the distribution system is referred to as an extendedservice set (ESS).

FIG. 2 illustrates an independent BSS which is a wireless communicationsystem according to another embodiment of the present invention. Forconvenience of description, another embodiment of the present inventionis described through the wireless LAN system. In the embodiment of FIG.2, duplicative description of parts, which are the same as or correspondto the embodiment of FIG. 1, will be omitted.

Since a BSS3 illustrated in FIG. 2 is the independent BSS and does notinclude the AP, all stations STA6 and STA7 are not connected with theAP. The independent BSS is not permitted to access the distributionsystem and forms a self-contained network. In the independent BSS, therespective stations STA6 and STA7 may be directly connected with eachother.

FIG. 3 is a block diagram illustrating a configuration of a station 100according to an embodiment of the present invention.

As illustrated in FIG. 3, the station 100 according to the embodiment ofthe present invention may include a processor 110, a transceiver 120, auser interface unit 140, a display unit 150, and a memory 160.

First, the transceiver 120 transmits and receives a wireless signal suchas a wireless LAN physical layer frame, or the like and may be embeddedin the station 100 or provided as an exterior. According to theembodiment, the transceiver 120 may include at least one transmit andreceive module using different frequency bands. For example, thetransceiver 120 may include transmit and receive modules havingdifferent frequency bands such as 2.4 GHz, 5 GHz, and 60 GHz. Accordingto an embodiment, the station 100 may include a transmit and receivemodule using a frequency band of 6 GHz or more and a transmit andreceive module using a frequency band of 6 GHz or less. The respectivetransmit and receive modules may perform wireless communication with theAP or an external station according to a wireless LAN standard of afrequency band supported by the corresponding transmit and receivemodule. The transceiver 120 may operate only one transmit and receivemodule at a time or simultaneously operate multiple transmit and receivemodules together according to the performance and requirements of thestation 100. When the station 100 includes a plurality of transmit andreceive modules, each transmit and receive module may be implemented byindependent elements or a plurality of modules may be integrated intoone chip.

Next, the user interface unit 140 includes various types of input/outputmeans provided in the station 100. That is, the user interface unit 140may receive a user input by using various input means and the processor110 may control the station 100 based on the received user input.Further, the user interface unit 140 may perform output based on acommand of the processor 110 by using various output means.

Next, the display unit 150 outputs an image on a display screen. Thedisplay unit 150 may output various display objects such as contentsexecuted by the processor 110 or a user interface based on a controlcommand of the processor 110, and the like. Further, the memory 160stores a control program used in the station 100 and various resultingdata. The control program may include an access program required for thestation 100 to access the AP or the external station.

The processor 110 of the present invention may execute various commandsor programs and process data in the station 100. Further, the processor110 may control the respective units of the station 100 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 110 may execute the program foraccessing the AP stored in the memory 160 and receive a communicationconfiguration message transmitted by the AP. Further, the processor 110may read information on a priority condition of the station 100 includedin the communication configuration message and request the access to theAP based on the information on the priority condition of the station100. The processor 110 of the present invention may represent a maincontrol unit of the station 100 and according to the embodiment, theprocessor 110 may represent a control unit for individually controllingsome component of the station 100, for example, the transceiver 120, andthe like. The processor 110 may be a modulator and/or demodulator whichmodulates wireless signal transmitted to the transceiver 120 anddemodulates wireless signal received from the transceiver 120. Theprocessor 110 controls various operations of wireless signaltransmission/reception of the station 100 according to the embodiment ofthe present invention. A detailed embodiment thereof will be describedbelow.

The station 100 illustrated in FIG. 3 is a block diagram according to anembodiment of the present invention, where separate blocks areillustrated as logically distinguished elements of the device.Accordingly, the elements of the device may be mounted in a single chipor multiple chips depending on design of the device. For example, theprocessor 110 and the transceiver 120 may be implemented while beingintegrated into a single chip or implemented as a separate chip.Further, in the embodiment of the present invention, some components ofthe station 100, for example, the user interface unit 140 and thedisplay unit 150 may be optionally provided in the station 100.

FIG. 4 is a block diagram illustrating a configuration of an AP 200according to an embodiment of the present invention.

As illustrated in FIG. 4, the AP 200 according to the embodiment of thepresent invention may include a processor 210, a transceiver 220, and amemory 260. In FIG. 4, among the components of the AP 200, duplicativedescription of parts which are the same as or correspond to thecomponents of the station 100 of FIG. 2 will be omitted.

Referring to FIG. 4, the AP 200 according to the present inventionincludes the transceiver 220 for operating the BSS in at least onefrequency band. As described in the embodiment of FIG. 3, thetransceiver 220 of the AP 200 may also include a plurality of transmitand receive modules using different frequency bands. That is, the AP 200according to the embodiment of the present invention may include two ormore transmit and receive modules among different frequency bands, forexample, 2.4 GHz, 5 GHz, and 60 GHz together. Preferably, the AP 200 mayinclude a transmit and receive module using a frequency band of 6 GHz ormore and a transmit and receive module using a frequency band of 6 GHzor less. The respective transmit and receive modules may performwireless communication with the station according to a wireless LANstandard of a frequency band supported by the corresponding transmit andreceive module. The transceiver 220 may operate only one transmit andreceive module at a time or simultaneously operate multiple transmit andreceive modules together according to the performance and requirementsof the AP 200.

Next, the memory 260 stores a control program used in the AP 200 andvarious resulting data. The control program may include an accessprogram for managing the access of the station. Further, the processor210 may control the respective units of the AP 200 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 210 may execute the program foraccessing the station stored in the memory 260 and transmitcommunication configuration messages for one or more stations. In thiscase, the communication configuration messages may include informationabout access priority conditions of the respective stations. Further,the processor 210 performs an access configuration according to anaccess request of the station. The processor 210 may be a modulatorand/or demodulator which modulates wireless signal transmitted to thetransceiver 220 and demodulates wireless signal received from thetransceiver 220. The processor 210 controls various operations such asradio signal transmission/reception of the AP 200 according to theembodiment of the present invention. A detailed embodiment thereof willbe described below.

FIG. 5 is a diagram schematically illustrating a process in which a STAsets a link with an AP.

Referring to FIG. 5, the link between the STA 100 and the AP 200 is setthrough three steps of scanning, authentication, and association in abroad way. First, the scanning step is a step in which the STA 100obtains access information of BSS operated by the AP 200. A method forperforming the scanning includes a passive scanning method in which theAP 200 obtains information by using a beacon message (S101) which isperiodically transmitted and an active scanning method in which the STA100 transmits a probe request to the AP (S103) and obtains accessinformation by receiving a probe response from the AP (S105).

The STA 100 that successfully receives wireless access information inthe scanning step performs the authentication step by transmitting anauthentication request (S107 a) and receiving an authentication responsefrom the AP 200 (S107 b). After the authentication step is performed,the STA 100 performs the association step by transmitting an associationrequest (S109 a) and receiving an association response from the AP 200(S109 b).

Meanwhile, an 802.1X based authentication step (S111) and an IP addressobtaining step (S113) through DHCP may be additionally performed. InFIG. 5, the authentication server 300 is a server that processes 802.1Xbased authentication with the STA 100 and may be present in physicalassociation with the AP 200 or present as a separate server.

When changing the physical layer frame format of a wireless signalconventionally used to enhance the performance of wirelesscommunication, coexistence with a wireless communication terminal thatdoes not support a formatted physical layer frame is a problem. At thistime, the changed physical layer frame is referred to as a non-legacyphysical layer frame, and an existing wireless communication terminalthat does not support the changed physical layer frame is referred to asa legacy wireless communication terminal. Specifically, when anon-legacy wireless communication terminal transmits a non-legacyphysical layer frame, a legacy wireless communication terminal that doesnot support non-legacy physical layer frames may not decode informationon non-legacy physical layer frames. Therefore, the legacy wirelesscommunication terminal may not know the length of the physical layerframe transmitted by the non-legacy wireless communication terminal, sothat the legacy wireless communication terminal may indefinitely sensethe channel. In addition, a transmission collision may occur between thelegacy wireless communication terminal and the non-legacy wirelesscommunication terminal, resulting in a decrease in transmissionefficiency.

To solve this problem, the non-legacy wireless communication terminalmay transmit signaling information decodable by a legacy wirelesscommunication terminal through a physical layer frame. Signalinginformation decodable by a legacy wireless communication terminal, whichis transmitted through a physical layer frame, is also referred to asL-SIG. At this time, after receiving the data value of the signaltransmitted after L-SIG, the non-legacy wireless communication terminalmay determine that the physical layer frame is a non-legacy physicallayer frame. Thus, the efficiency that a non-legacy wirelesscommunication terminal determines whether there is a non-legacy physicallayer is low. Therefore, when the non-legacy physical layer frameincludes L-SIG, a method for quickly determining whether there is anon-legacy physical layer frame by the non-legacy wireless communicationterminal is needed. This will be described with reference to FIGS. 6 to23.

FIG. 6 shows a structure of an IEEE 802.11ac physical layer framesupporting a legacy wireless LAN mode.

As shown in FIG. 6, the 11ac physical layer frame includes a legacypreamble, a Very High Throughput (VHT) preamble, and VHT data. Thelegacy preamble may be decoded in a legacy wireless communicationterminal such as IEEE 802.11a (hereinafter referred to as 11a) wirelesscommunication terminal and the 11a wireless communication terminalprotects the 11ac physical layer frame based on information extractedfrom the legacy preamble. Meanwhile, the 11ac wireless communicationterminal obtains length information indicating the length T of thephysical layer frame from the legacy preamble of the 11ac physical layerframe. Therefore, the VHT preamble (for example, VHT-SIG) of the 11acphysical layer frame may not include the length information.

FIG. 7 shows a preamble structure of IEEE 802.11n, 11a and 11ac physicallayer frames.

As in the embodiment of FIG. 7, the 11a physical layer frame includes alegacy preamble and legacy data (L-Data). The legacy preamble includes alegacy short training field (L-STF), a legacy long training field(L-LTF), and a legacy signal field (L-SIG), and among them, L-SIG ismodulated using Binary Phase Shift Keying (BPSK). On the other hand, the11n/ac packet includes a legacy preamble as in the 11a packet, andincludes the recognizable information of the 11n/ac terminal as aseparate preamble after the L-SIG (i.e., an HT preamble and a VHTpreamble). The wireless communication terminal supporting 11a extractsrate information and length information included in the L-SIG of thephysical layer frame. The wireless communication terminal supporting 11aregards a portion after L-SIG as legacy data L-Data and decodes theportion after L-SIG based on the rate information and lengthinformation. The legacy data L-Data is modulated using any one of BPSK,Quadrature Binary Phase Shift Keying (QPSK), 16-Quadrature AmplitudeModulation (QAM), and 64-QAM.

On the other hand, the physical layer frame in 11n may be distinguishedfrom the physical layer frame in 11a (IEEE 802.11g physical layer framein the case of a 2.4 GHz band) based on a modulation technique used fora High Throughput (HT) preamble after a legacy preamble. Referring toFIG. 7, initial symbols 310 n and 320 n constituting the HT-SIG (HT-SIG1and HT-SIG2) of the HT preamble in the 11n physical layer frame aremodulated through a modulation technique not used for 11a packets, thatis, Quadrature Binary Phase Shift Keying (QBPSK). The wirelesscommunication terminal supporting 11n identifies the modulationtechnique used for the first symbol 310 after the legacy preamble of thereceived physical layer frame. If the first symbol 310 is modulated withQBPSK, the wireless communication terminal supporting 11n recognizesthat the corresponding physical layer frame is an 11n physical layerframe. The wireless communication terminal supporting 11n additionallychecks whether the modulation technique of the QBPSK is used for thesecond symbol 320 after the legacy preamble of the physical layer frame,thereby increasing the reliability of physical layer frameidentification.

Thus, the discrimination of the format of the physical layer frame basedon the modulation technique used in the preamble of the physical layerframe by the wireless communication terminal is referred to as autodetection. The wireless communication terminal supporting 11n may useauto detection, and without the Cyclical Redundancy Check (CRC) for theHT-SIG of the physical layer frame, determine whether the correspondingphysical layer frame is an 11n physical layer frame. Through autodetection, when the received physical layer frame is not an 11n physicallayer frame, the wireless communication terminal supporting 11n mayreduce power consumption due to an unnecessary decoding process. Also,through auto detection, the wireless communication terminal supporting11n may reduce the data transmission/reception delay, for an example, adelay due to 11a fallback decision.

In a similar manner, the wireless communication terminal may distinguishthe 11ac physical layer frame from the 11a physical layer frame and the11n physical layer frame based on the modulation technique used for theVHT preamble after the legacy preamble. However, the preamble of the11ac physical layer frame should minimize the influence on the autodetection process of the 11n terminal described above. That is, amodulation technique for preventing the 11n terminal from recognizingthe physical layer frame as the 11n physical layer frame in the firstsymbol 310 c after the legacy preamble may be used in the 11ac physicallayer frame. Accordingly, referring to FIG. 7, the first symbol 310 cafter the legacy preamble in the 11ac physical layer frame is modulatedwith BPSK and the second symbol 320 c is modulated with QBPSK,respectively. At this time, the first symbol 310 c constitutes theVHT-SIG-A1 of the VHT preamble and the second symbol 320 c constitutesthe VHT-SIG-A2 of the VHT preamble.

Based on the modulation technique used for the first symbol 310 and thesecond symbol 320 after the legacy preamble of the received physicallayer frame, the wireless communication terminal supporting 11acdetermines whether the physical layer frame is an 11ac physical layerframe. Specifically, the wireless communication terminal supporting 11acmay distinguish the 11n physical layer frame from the non-11n physicallayer frame based on the modulation technique used in the first symbol310, and may distinguish the 11a physical layer frame and the 11acphysical layer frame from the non-11n physical layer frame based on themodulation technique used in the second symbol 310.

FIG. 8 shows a symbol specific modulation technique of L-SIG, HT-SIG,and VHT-SIG-A for auto detection between 802.11a/n/ac physical layerframes.

First, the L-SIGs of the 11a, 11n and 11ac physical layer frames aremodulated with BPSK. The wireless communication terminal supporting 11areceives the physical layer frame and extracts the L-SIG of the physicallayer frame. At this time, the wireless communication terminalsupporting 11a regards symbols after L-SIG as data. Therefore, even whenthe wireless communication terminal supporting 11a receives the 11nphysical layer frame or the 11ac physical layer frame, the wirelesscommunication terminal supporting 11a recognizes the received physicallayer frame as an 11a physical layer frame. The wireless communicationterminal supporting 11a extracts the length information from the L-SIGof the received physical layer frame. The wireless communicationterminal supporting 11a defers the transmission/reception operation bythe time corresponding to the length information. Thus, the wirelesscommunication terminal supporting 11a protects the received 11n physicallayer frame or 11ac physical layer frame.

The HT-SIG, which is the first symbol 310 n and the second symbol 320 nafter the L-SIG of the 11n physical layer frame, is modulated withQBPSK. The wireless communication terminal supporting 11n checks themodulation technique used for the first symbol after the legacy preambleof the received physical layer frame. When the first symbol is modulatedwith QBPSK, the wireless communication terminal supporting 11ndetermines that the physical layer frame is an 11n physical layer frame.At this time, the wireless communication terminal may determine themodulation technique through the distribution between the I/Q channelsof the constellation points of subcarriers where each data transmissionis performed. In addition, the wireless communication terminalsupporting 11n may additionally confirm whether or not the modulationtechnique of QBPSK is used for the second symbol after the legacypreamble of the received physical layer frame. Thus, the wirelesscommunication terminal supporting 11n may increase the reliability of11n physical layer frame identification.

The first symbol 310 c after the L-SIG of the 11ac physical layer frameis modulated with BPSK, and the second symbol 320 c is modulated withQBPSK. Specifically, the first symbol 310 c and the second symbol 320 cof the VHT-SIG-A of the 11ac physical layer frame are modulated withBPSK and QBPSK, respectively. Based on the modulation technique used forthe first symbol and the second symbol after the legacy preamble of thereceived physical layer frame, the wireless communication terminalsupporting 11ac determines whether the corresponding physical layerframe is an 11ac physical layer frame. When the second symbol ismodulation with QBPSK, the wireless communication terminal supporting11ac should determine whether the corresponding physical layer frame isthe 11n physical layer frame through the first symbol to clearlydetermine the format of the physical layer frame.

FIG. 9 shows a structure of an IEEE 802.11ax physical layer frameaccording to an embodiment of the present invention.

In an embodiment of the present invention, a non-legacy wireless LANmode may represent an IEEE 802.11ax wireless LAN mode, and a legacywireless LAN mode may represent a wireless LAN mode such as 11a, 11g,11n, and 11ac, i.e., a legacy, compared to the 11ax. In addition, theformat of the physical layer frame in the present invention may indicateinformation on the wireless LAN communication standard mode used in thephysical layer frame. Specifically, the information on the wireless LANcommunication standard mode may indicate information on a communicationstandard mode of IEEE 802.11a/g/n/ac/ax.

In the embodiment of FIG. 9, a non-legacy physical layer frame (i.e.,11ax physical layer frame) may be designed with a new physical layerframe structure decodable only by a non-legacy wireless communicationterminal (such as an 11ax terminal).

As described above, the legacy preamble may include L-STF, L-LTF, andL-SIG for compatibility with a legacy terminal. The non-legacy physicallayer frame may include a High Efficiency (HE) preamble and HE dataafter L-SIG. The HE preamble includes HE-SIGs consisting of at least oneSIG (HE-SIG-1, HE-SIG-2, . . . , HE-SIG-n), HE-STF, and HE-LTFs fornon-legacy wireless LAN operation. At this time, SIG refers to asignaling field indicating signaling information of a physical layerframe. Also, various arrangements such as the number and positions ofHE-SIG/STF/LTF in the HE preamble are possible. In an embodiment of thepresent invention, the HE preamble may be referred to as a non-legacypreamble.

At this time, when the legacy physical layer frame and the non-legacyphysical layer frame coexist, there is a need for an HE preamblestructure in which a non-legacy wireless communication terminal mayautomatically detect information on a non-legacy physical layer framewhile minimizing the influence on a legacy wireless communicationterminal.

FIG. 10 shows the structures of a legacy physical layer frame and anon-legacy physical layer frame according to an embodiment of thepresent invention.

As described above, the legacy physical layer frame may include aphysical layer frame of IEEE 802.11a/g/n/ac. In addition, a non-legacyphysical layer frame may represent an IEEE 802.11ax physical layerframe.

The HE preamble of the non-legacy physical layer frame is composed of aplurality of symbols. In the present invention, a symbol indicates anOrthogonal Frequency Division Multiplexing (OFDM) symbol, and one symbolincludes a valid OFDM symbol section and a guard interval section. Inaddition, in FIG. 10, one symbol of the preamble section may have alength of 4 us, but the present invention is not limited thereto, andthe length of the symbol may vary depending on the kind of DiscreteFourier Transform (DFT) used. In an embodiment below, the first symbolafter the L-SIG of the non-legacy physical layer frame is referred to asa first symbol 310 x, the second symbol is referred to as a secondsymbol 320 x, and the third symbol is referred to as a third symbol 330x. That is, the first symbol 310 x, the second symbol 320 x, and thethird symbol 330 x represent the first symbol, the second symbol, andthe third symbol of the HE preamble, respectively.

In the embodiment of FIG. 10, the HE preamble may be divided into threeregions Region 1, Region 2, and Region 3 based on the preambles of 11nand 11ac physical layer frames. First, the first region Region 1 is afirst region after the L-SIG, and may include two symbols. In the firstregion, the 11a physical layer frame includes legacy data L-Data, the11n physical layer frame includes HT-SIG, and the 11ac physical layerframe includes VHT-SIG. Accordingly, the wireless communication terminaldemodulates the data in the first region of the 11a physical layerframe, and demodulates the HT-SIG and the VHT-SIG in the first region ofthe 11n physical layer frame and the 11ac physical layer frame. Asdescribed above, the legacy wireless communication terminal (11n and11ac terminals) capable of auto detection may determine 11n and/or 11acphysical layer frames based on the modulation technique used in thesymbols of the first region. Accordingly, the wireless legacycommunication terminal demodulates the physical layer frame based on theformat of the physical layer frame, i.e., the WLAN communicationstandard mode.

According to an embodiment of the present invention, the first symbol310 x and the second symbol 320 x included in the first region in thenon-legacy physical layer frame may be modulated with BPSK,respectively. Through this, the non-legacy physical layer frame mayminimize the influence on the auto detection performance of the wirelesscommunication terminal supporting 11n and the wireless communicationterminal supporting 11ac, which are legacy wireless communicationterminals. According to an embodiment of the present invention, BPSKmodulation may be used for all the subcarriers of the first symbol 310 xand the second symbol 320 x, but a modulation technique other than BPSKmay be used for some subcarriers (e.g., subcarriers of an even/oddindex). However, if another modulation technique is used in somesubcarriers, since the auto detection performance of the 11n/ac wirelesscommunication terminal may be degraded, it is possible to use anothermodulation technique only in the specified some ranges.

The second region Region 2 following the first region Region 1 mayinclude at least one symbol. In the second region, the 11a physicallayer frame includes legacy data L-Data, the 11n physical layer frameincludes HT-STF, and the 11ac physical layer frame includes VHT-STF,respectively. Accordingly, in the second region of the 11a physicallayer frame, the wireless communication terminal demodulates the data inthe same manner as the first region, and in the second region of the 11nphysical layer frame and the 11ac physical layer frame, detects the STFbased on the repetition characteristics of the time domain signal. Atthis time, the symbols of the second region of the 11n physical layerframe and the 11ac physical layer frame are modulated with QPSK.

As in the above embodiment, when the symbols of the first region of thenon-legacy physical layer frame, i.e., the first symbol 310 x and thesecond symbol 320 x, are modulated with BPSK, the wireless communicationterminal supporting 11n and 11ac may determine the correspondingphysical layer frame as a 11a physical layer frame. Therefore, themodulation technique used for the symbol of the second region of thephysical layer frame has little effect on the auto detection process ofthe 11n terminal and the 11ac terminal. Therefore, according to anembodiment of the present invention, a variety of modulation techniquesmay be used for the symbol, i.e., the third symbol 330 x, of the secondregion of the non-legacy physical layer frame. For example, modulationsuch as BPSK, QBPSK, or QPSK may be used for the third symbol 330 x ofthe non-legacy physical layer frame. According to one embodiment, thethird symbol 330 x of the non-legacy physical layer frame may bemodulated with QBPSK. In such a way, when QBPSK having orthogonalcharacteristics with respect to BPSK is used for the modulation of thethird symbol 330 x, the non-legacy physical layer frame may bedistinguished from the 11a/g physical layer frame. At this time, thenon-legacy terminal confirms that the first symbol, the second symbol,and the third symbol after the L-SIG of a received packet are modulatedwith BPSK, BPSK, and QBPSK, respectively, so that it may determine thatthe corresponding physical layer frame is a non-legacy physical layerframe. However, in an embodiment of the present invention, the autodetection method of the non-legacy wireless communication terminal isnot limited thereto, and the non-legacy wireless communication terminalmay auto-detect the non-legacy physical layer frame based on variousembodiments.

The third region Region 3 represents the remaining preamble sectionafter the second region Region 2. In the third region Region 3, the 11nphysical layer frame includes HT-LTF and the 11ac physical layer frameincludes VHT-LTF and VHT-SIG-B. The symbols in the third region aremodulated with BPSK. According to one embodiment, the third symbol 330 xof the non-legacy physical layer frame may be modulated with QBPSK. Thenon-legacy wireless communication terminal may auto-detect thecorresponding physical layer frame based on the modulation techniqueused in the third region of the non-legacy physical layer frame. At thistime, at least some of the modulation technique and the preamblestructure of the first region and the second region of the non-legacyphysical layer frame may be set to be the same as that of the legacyphysical layer frame.

FIGS. 11 to 13 show structures of a preamble of a non-legacy physicallayer frame according to an embodiment of the present invention.

In each of the embodiments of FIGS. 11 to 13, the same or correspondingparts as those of the embodiment of the previous drawings are notdescribed.

FIG. 11 shows an embodiment of a preamble configuration of a non-legacyphysical layer frame according to the present invention. Referring toFIG. 11, the non-legacy physical layer frame includes a legacy preambleand an HE preamble 300 a. The HE preamble 300 a includes a HighEfficiency signal field (HE-SIG), a High Efficiency short training field(HE-STF), and a High Efficiency long training field (HE-LTF). In anembodiment of the present invention, the HE-SIG, the HE-STF, and theHE-LTF may be referred to as a non-legacy SIG, a non-legacy STF and anon-legacy LTF, respectively.

According to the basic structure of FIG. 11, the HE-SIG may include afirst symbol 310 x, a second symbol 320 x, and a third symbol 330 x.According to the embodiment of FIG. 11, the first symbol 310 x and thesecond symbol 320 x are modulated with BPSK, and the third symbol 330 xis modulated with QBPSK. At this time, the non-legacy physical layerframe may be distinguished from the 11n physical layer frame through thefirst symbol 310 x modulated with BPSK, and may be distinguished fromthe 11ac physical layer frame through the second symbol 320 x modulatedwith BPSK. In addition, the non-legacy physical layer frame may bedistinguished from the 11a/g physical layer frame through the thirdsymbol 330 x modulated with QBPSK. In such a way, the HE-SIG of thenon-legacy physical layer frame may be composed of three or moresymbols, and may further include an additional SIG if necessary.

FIG. 12 shows another embodiment of a preamble configuration of anon-legacy physical layer frame according to the present invention.According to another embodiment of the present invention, the HE-SIG ofa non-legacy physical layer frame may have a variable length. However,FIG. 12 shows an HE preamble 300 a having an HE-SIG composed of threesymbols, and an HE preamble 300 b having an HE-SIG composed of twosymbols.

The HE-SIG may be set to a variable length according to variousembodiments. As described later, the HE-SIG may be composed of aplurality of SIGs, and the HE-SIG length may vary depending on whetheran additional SIG is included or not. Also, HE-SIG may have a variablelength depending on the frequency band in which the correspondingphysical layer frame is used. For example, the HE preamble 300 b of thenon-legacy physical layer frame in the first frequency band (e.g., the2.4 GHz band) where no 11ac packet is transmitted may include an HE-SIGcomposed of two symbols 310 x and 320 x. According to an embodiment, thefirst symbol 310 x constituting the HE-SIG of the HE preamble 300 b maybe modulated through BPSK and the second symbol 320 x may be modulatedthrough QBPSK. When the first symbol 310 x and the second symbol 320 xof the HE preamble 300 b of the non-legacy physical layer frame aremodulated in the same manner as those of the 11ac physical layer frame,the wireless communication terminal may determine the non-legacyphysical layer frame using the same auto detection method of the 11acphysical layer frame in the first frequency band (2.4 GHz band). On theother hand, in the second frequency band (i.e., the 5 GHz band) in whichthe 11ac physical layer frame is transmitted, the HE-SIG of the HEpreamble 300 a of a non-legacy physical layer frame may further includean additional SIG composed of the third symbol 330 x in the HE-SIG usedin the HE preamble 300 b in the first frequency band. At this time, thenon-legacy wireless communication terminal may determine whether thenon-legacy wireless communication terminal is a non-legacy physicallayer frame through the modulation technique used in the third symbol330 x of the HE preamble 300 a or the transmission data of thecorresponding symbol. Meanwhile, the wireless communication terminalsupporting the 11ac, which receives the HE preamble 300 a of thenon-legacy physical layer frame, may determine that the correspondingphysical layer frame is not the 11ac physical layer frame through theerror occurring in the decoding process of the VHT-SIG1.

Moreover, although it is shown in FIG. 12 that the length of the HE-SIGvaries by two symbols or three symbols, the present invention is notlimited thereto and the HE-SIG may be set to a length longer than that.

In order to improve the reliability of the non-legacy wirelesscommunication terminal to auto-detect non-legacy physical layer frames,the non-legacy wireless communication terminal may transmit signalinginformation based on the L-SIG to the first symbol of the non-legacysignaling field of the non-legacy physical layer frame. At this time,the signaling information based on the L-SIG is referred to as RL-SIG.RL-SIG may be modulated by the same modulation method as L-SIG. RL-SIGmay be the same signaling information as L-SIG. RL-SIG may be signalinginformation obtained by modifying at least one of the size and the phaseof L-SIG. This will be described with reference to FIGS. 13 to 22.

FIG. 13 shows a structure of a preamble of a non-legacy physical layerframe including a repeated L-SIG according to an embodiment of thepresent invention.

As described above, RL-SIG may be the same signaling information asL-SIG. At this time, the non-legacy wireless communication terminal maymodulate the RL-SIG with the same modulation method as the L-SIG. Inthis case, the non-legacy wireless communication terminal repeatedlytransmits the same signal as the L-SIG. For example, the non-legacywireless communication terminal may transmit the RL-SIG including thesame signaling information as the L-SIG by modulating the first symbolof the non-legacy signaling field of the non-legacy physical layer framewith BPSK. At this time, the length of the RL-SIG symbol is 4 us.

In addition, the non-legacy wireless communication terminal may modulatethe second symbol of the non-legacy signaling field with BPSK. Throughthe second symbol of the non-legacy signaling field, the legacy wirelesscommunication terminal may distinguish the 11ac physical layer framefrom the non-legacy physical layer frame. This will be described indetail with reference to FIG. 14.

FIG. 14 shows an operation of auto-detecting a non-legacy physical layerframe including a repeated L-SIG by a wireless communication terminalaccording to an embodiment of the present invention.

The wireless communication terminal determines whether the first symbolSYM-1 after L-SIG is modulated with QBPSK. When the first symbol SYM-1after L-SIG is modulated with QBPSK, the wireless communication terminaldetermines the received physical layer frame as an 11n physical layerframe.

When the first symbol SYM-1 after L-SIG is modulated with BPSK, thewireless communication terminal determines whether the L-SIG isrepeatedly transmitted and the second symbol SYM-2 after L-SIG ismodulated with BPSK.

If the L-SIG is repeatedly transmitted and the second symbol SYM-2 afterL-SIG is modulated with BPSK, the wireless communication terminaldetermines the validity of the information included in the L-SIG.Specifically, the wireless communication terminal may check the validityof at least one of the length information, the parity information, andthe transmission rate information included in the L-SIG.

If the information included in the L-SIG is valid, the wirelesscommunication terminal determines the received physical layer frame as anon-legacy physical layer frame.

In addition, non-legacy physical layer frames do not affect the autodetection of the legacy wireless communication terminal. Specifically,since the wireless communication terminal supporting 11a of the legacywireless communication terminal may not decode the second symbol afterthe L-SIG of the non-legacy physical layer frame, it processes a signalafter the L-SIG as an error.

Also, since the first symbol SYM-1 after the L-SIG of the non-legacyphysical layer frame is not modulated with QBPSK, a wirelesscommunication terminal supporting 11n among legacy wirelesscommunication terminals does not determine the non-legacy physical layerframe as the 11n physical layer frame.

Also, when the second symbol SYM-1 after the L-SIG of the non-legacyphysical layer frame is modulated with QBPSK, a wireless communicationterminal supporting 11ac among legacy wireless communication terminalsdoes not determine the non-legacy physical layer frame as the 11acphysical layer frame.

Also, the legacy wireless communication terminal does not approach thefrequency band in which the physical layer frame is transmitted based onthe L-LENGTH included in the L-SIG.

The non-legacy wireless communication terminal may increase thedetection speed of the physical layer frame and enhance the reliabilityof non-legacy physical layer frame detection by transmitting the RL-SIG.The RL-SIG does not affect the auto detection of legacy wirelesscommunication terminals. However, when the RL-SIG is used only for autodetection, the wireless communication terminal must transmit symbolsincluding no information each time a non-legacy physical layer frame istransmitted. Therefore, when using the RL-SIG, a method is needed forthe wireless communication terminal to transmit additional information.This will be described with reference to FIGS. 15 to 22.

FIG. 15 shows that a non-legacy physical layer frame signals the formatof a non-legacy physical layer frame according to an embodiment of thepresent invention.

The wireless communication terminal may signal the format of thenon-legacy physical layer frame through the modulation method of thethird symbol after the L-SIG of the non-legacy physical layer frame.Specifically, the modulation method of the third symbol after L-SIG mayindicate the format of the non-legacy signaling field. For example, theHE-SIG B field for signaling information for each of the plurality ofwireless communication terminals of FIG. 15 may not be transmittedaccording to the transmission mode. Therefore, the modulation method ofthe third symbol after L-SIG may indicate whether the HE-SIG B field istransmitted. In yet another specific embodiment, the modulation methodof the third symbol after L-SIG may represent the format of HE-SIG A.

At this time, the wireless communication terminal may signal the formatof the non-legacy physical layer frame by modulating the third symbolafter the L-SIG of the non-legacy physical layer frame with QBPSK. In aspecific embodiment, the wireless communication terminal may signal theformat of a non-legacy physical layer frame for long range transmissionby modulating the third symbol after L-SIG with QBPSK.

In yet another specific embodiment, the wireless communication terminalmay signal the format of the non-legacy physical layer frame bymodulating the third symbol after the L-SIG of the non-legacy physicallayer frame with QPSK. When the wireless communication terminalmodulates the third symbol after the L-SIG with QPSK, the capacity oftransmission information per symbol becomes large, so that the wirelesscommunication terminal may increase the information transmissionefficiency.

The wireless communication terminal may signal additional informationthrough the RL-SIG when modifying the signal characteristics of theL-SIG to generate the RL-SIG. Specifically, the wireless communicationterminal may generate RL-SIG by modifying at least one of the magnitudeand the phase of a signal representing L-SIG. This will be describedwith reference to FIGS. 16 to 22.

FIG. 16 shows data sub-carriers and pilot sub-carriers of L-SIGaccording to an embodiment of the present invention.

The L-SIG includes a total of 24-bit fields such as an L_RATE fieldindicating a transmission rate, an L_LENGTH field indicating a length ofa physical layer frame after L_SIG, a Parity field for error checking, aTail field, and Reserved Bits. The wireless communication terminalgenerates a 48-bit code bit through a ½ rate BCC technique. Such a48-bit code bit may be composed of 48 BPSK modulation data. The wirelesscommunication terminal transmits 48 BPSK modulation data in one OFDMsymbol through 48 subcarriers. At this time, channel estimation isnecessary for demodulation of code bits. Therefore, the wirelesscommunication terminal transmits the pilot signal for channel estimationthrough four subcarriers. At this time, the pilot subcarriers arereferred to as pilot subcarriers, and the subcarriers for transmittingdata are referred to as data subcarriers. The positions of the pilotsubcarriers of the L-SIG are index values −21, −7, 7, and 21.

The wireless communication terminal may transmit the same signal as thesignal including the L-SIG as the signal including the RL-SIG. Forconvenience of explanation, a signal including L-SIG is referred to asan L-SIG signal, and a signal including RL-SIG is referred to as RL-SIG.At this time, the wireless communication terminal may transmit theRL-SIG by changing the position of the pilot subcarrier of the RL-SIGsignal to be different from the position of the pilot subcarrier of theL-SIG signal. Therefore, the wireless communication terminal may signalinformation through the location of the pilot subcarrier of the RL-SIG.This will be described again with reference to FIG. 22.

FIG. 17 shows an RL-SIG signaling information through a signalcharacteristic of a frequency region divided into a plurality ofsections according to an embodiment of the present invention.

The wireless communication terminal may generate the RL-SIG by modifyingat least one of L-SIG data, the locations of the pilot subcarriers andnumber of the pilot subcarriers. However, the wireless communicationterminal receiving the non-legacy physical layer frame should be able todetermine that the RL-SIG is the signaling information generated basedon the L-SIG. Therefore, information should be transmitted withoutdegrading the signal characteristics of the L-SIG.

In a specific embodiment, the wireless communication terminal may signalinformation based on a modification in one or more frequency sectionspecific signals that the RL-SIG includes with respect to one or morefrequency section specific signals, which is included in the L-SIG. Atthis time, the modification of the signal may indicate at least one ofshifting the phase of the signal and changing the amplitude of thesignal. For this, the wireless communication terminal divides the L-SIGsignal into a plurality of frequency sections Part_i and shifts theta_ithe phase of a signal in at least any one section among the plurality ofdivided frequency sections to generate RL-SIG. In addition, the wirelesscommunication terminal may change A_i the magnitude of a signal in atleast any one section among the plurality of divided frequency sectionsto generate RL-SIG.

At this time, the wireless communication terminal may shift to allow aphase value of a frequency section specific signal of RL-SIG to have 0or 180 degrees. If the phase section specific signal phase value is 0 or180 degrees (when the frequency section specific signal is multiplied by+1 or −1), it is modulated with BPSK. Therefore, frequency sectionspecific phase shift of RL-SIG signal does not affect auto detection of11n or 11ac. Specifically, the wireless communication terminalsupporting 11n or 11ac determines whether it is the 11n physical layerframe or the 11ac physical layer frame according to whether themodulation method after L-SIG is BPSK or QBPSK. If the phase shift ofthe frequency section specific signal is 0 or 180 degrees in RL-SIG, thewireless communication terminal supporting 11n or 11ac determines thatthe modulation method after L-SIG is BPSK. Therefore, it does not affectthe auto detection operation of the wireless communication terminalsupporting 11n or 11ac. If the wireless communication terminal applies aphase shift of 0 or 180 degrees to each frequency section of the RL-SIGsignal, the wireless communication terminal may transmit at least 1 bitof additional information through the RL-SIG signal.

When the wireless communication terminal transmits information based ona modification of a plurality of frequency section specific signalsincluded in the RL-SIG with respect to a plurality of frequency sectionspecific signals included in the L-SIG, the operation of detecting theRL-SIG by the wireless communication terminal receiving the non-legacyphysical layer frame should be modified. This will be described withreference to FIG. 18.

FIG. 18 shows an operation of detecting RL-SIG by a wirelesscommunication terminal according to an embodiment of the presentinvention.

The wireless communication terminal may compensate for the the signalmodification by performing each frequency section of the received signalto determine whether the received signal is an RL-SIG generated based onthe L-SIG. Further, when the received signal is RL-SIG, the wirelesscommunication terminal may obtain additional information based on thecompensation for the received signal. This is because the wirelesscommunication terminal transmitting the RL SIG may change the size foreach frequency section of the L-SIG signal or shifts the phase for eachfrequency section of the L-SIG signal, thereby generating the RL-SIGsignal.

The wireless communication terminal compensates the received signal foreach frequency section (S1801). Specifically, the wireless communicationterminal may compensate for the changed size compared to the L-SIG foreach frequency section of the received signal. In addition, the wirelesscommunication terminal may compensate for the shifted phase compared tothe L-SIG for each frequency section of the received signal. At thistime, the wireless communication terminal may compensate for achangeable size or a shiftable phase size in order for informationtransmission. Specifically, the number of changeable sizes or the numberof shiftable sizes for each frequency section of the L-SIG signal may beplural in order for generation of the RL-SIG signal. At this time, thewireless communication terminal may apply all the compensation for theapplicable signal modification to each frequency section.

For example, when applying the 0-degree or 180-degree phase shift to theL-SIG to generate the RL-SIG, the wireless communication terminalmultiplies a value selected by 1-bit information of +1 or −1 by eachfrequency section of an L-SIG signal. At this time, the wirelesscommunication terminal receiving the signal may compensate the signal bymultiplying +1 or multiplying by −1 for each frequency section. Forthis, the range of a phase shift of the signal for the wirelesscommunication terminal to signal information through the RL-SIG may bepredetermined. In addition, the range of a changeable signal magnitudefor the wireless communication terminal to signal information throughthe RL-SIG may be predetermined.

The wireless communication terminal compares the compensated signal withL-SIG and determines whether the received signal is RL-SIG (S1803).Specifically, when the compensated signal is equal to L-SIG, thewireless communication terminal may determine the received signal asRL-SIG. As described above, the number of sizes of a shiftable phase maybe plural or the magnitude of a changeable signal may be plural. Inaddition, the wireless communication terminal may apply all thecompensation for an available signal modification to each frequencysection. At this time, the wireless communication terminal may determinewhich compensation method among applied compensation methods isidentical to the L-SIG signal of the corresponding frequency section.For example, when applying the 0-degree or 180-degree phase shift to theL-SIG to generate the RL-SIG, the wireless communication terminalmultiplies a value selected by 1-bit information of +1 or −1 by eachfrequency section of an L-SIG signal. At this time, the wirelesscommunication terminal receiving the signal may multiply each frequencysection by +1 to compensate the signal, and then compare the compensatedsignal with the signal of the corresponding frequency section of theL-SIG signal. In addition, the wireless communication terminal receivingthe signal may multiply each frequency section by −1 to compensate thesignal, and then compare the compensated signal with the signal of thecorresponding frequency section of the L-SIG signal.

When the wireless communication terminal determined that the receivedsignal is RL-SIG, the wireless communication terminal obtains signalinginformation of the RL-SIG based on the signal compensation (S1805). Atthis time, the wireless communication terminal may obtain the signalinginformation of the RL-SIG based on at least one of a magnitude change ofa frequency section specific signal and a phase shift of a signal.Specifically, the wireless communication terminal may obtain thesignaling information of the RL-SIG based on a value used for frequencysection specific signal compensation. In a specific embodiment, thewireless communication terminal may obtain the signaling information ofthe RL-SIG based on a signal magnitude used for frequency sectionspecific signal compensation. For example, the signal magnitude used forsection specific signal compensation may indicate the value of thesignaling information of the RL-SIG. In another specific embodiment, thewireless communication terminal may obtain the signaling information ofthe RL-SIG based on a phase shift value of a signal used for frequencysection specific signal compensation. For example, the phase shift valueof the signal used for section specific signal compensation may indicatethe value of the signaling information of the RL-SIG.

When the wireless communication terminal does not determine that thereceived signal is not the RL-SIG, the wireless communication terminaldetermines the received signal as a legacy packet. At this time, thewireless communication terminal starts an operation for detecting alegacy packet from the received signal.

As described above, the RL-SIG may be identical to the entire L-SIG inthe time domain. In another specific embodiment, the RL-SIG may includeonly a portion of the L-SIG signal in the time domain. In anotherspecific embodiment, the wireless communication terminal divides theL-SIG, in a time domain, into a plurality of sections having the samesize or a size having a rational number multiplication relationship, andchanges at least one of size and phase for each time section to generateRL-SIG. At this time, the wireless communication terminal may divide theL-SIG into a plurality of time sections in consideration of CP/GI. Thegeneration of the RL-SIG by modifying the L-SIG signal for each timesection will be described with reference to FIG. 19.

FIG. 19 shows an RL-SIG signaling information through a signalcharacteristic of a time domain divided into a plurality of sectionsaccording to an embodiment of the present invention. FIG. 19(a) shows apreamble signal of a physical layer frame transmitted by a wirelesscommunication terminal in a time domain. FIG. 19(b) shows that RL-SIG isgenerated by dividing an L-SIG signal into a plurality of time sectionsand changing the phase of the L-SIG signal and the magnitude of theL-SIG signal in each of the plurality of time sections.

Specifically, the wireless communication terminal may signal informationbased on a modification in one or more frequency section specificsignals that the RL-SIG includes with respect to one or more timesection specific signals, which is included in the L-SIG. At this time,the modification of the signal may indicate at least one of shifting thephase of the signal and changing the amplitude of the signal. For this,the wireless communication terminal divides the L-SIG signal into aplurality of time sections and shifts the phase theta_i of a signal inat least any one section among the plurality of divided time sections togenerate RL-SIG. In addition, the wireless communication terminal maychange the magnitude A_i of a signal in at least any one section amongthe plurality of divided time sections to generate RL-SIG.

When the wireless communication terminal signals information based on amodification of a plurality of time section specific signals included inthe RL-SIG with respect to a plurality of time section specific signalsincluded in the L-SIG, the operation of detecting the RL-SIG by thewireless communication terminal receiving the non-legacy physical layerframe should be changed.

At this time, the wireless communication terminal may compensate for thesignal modification by performing each time section of the receivedsignal to determine whether the received signal is an RL-SIG generatedbased on the L-SIG.

Specifically, the wireless communication terminal may compensate for thechanged size compared to the L-SIG for each time section of the receivedsignal. In addition, the wireless communication terminal may compensatefor the shifted phase compared to the L-SIG for each time section of thereceived signal. At this time, the wireless communication terminal maycompensate for a changeable size or a shiftable phase size in order forinformation transmission. Specifically, the number of changeable sizesor the number of shiftable sizes for each time section of the L-SIGsignal may be plural in order for generation of the RL-SIG signal. Atthis time, the wireless communication terminal may apply all thecompensation for the applicable signal modification to each timesection.

For example, when the wireless communication terminal apply the 0-degreeor 180-degree phase shift to the L-SIG to generate the RL-SIG, thewireless communication terminal multiplies a value selected by 1-bitinformation of +1 or −1 by each time section of an L-SIG signal. At thistime, the wireless communication terminal receiving the signal maycompensate the signal by multiplying +1 or multiplying by −1 for eachtime section. For this, the range of a phase shift of the signal for thewireless communication terminal to signal information through the RL-SIGmay be predetermined. In addition, the range of a changeable signalmagnitude for the wireless communication terminal to signal informationthrough the RL-SIG may be predetermined. For this, the range of a phaseshift of the signal for additional information may be predetermined inorder for the wireless communication terminal to generate the RL-SIGincluding additional information transmission. In addition, the range ofa changeable signal magnitude for the wireless communication terminal togenerate RL-SIG may be predetermined. The wireless communicationterminal compares the compensated signal with L-SIG and determineswhether the received signal is RL-SIG. Specifically, if the compensatedsignal is equal to L-SIG, the wireless communication terminal maydetermine the received signal as RL-SIG. As described above, the numberof sizes of a shiftable phase may be plural or the magnitude of achangeable signal may be plural. Accordingly, the wireless communicationterminal may apply all the compensation for an available signalmodification to each time section. At this time, the wirelesscommunication terminal may determine whether the compensated signal isidentical to the L-SIG signal of the corresponding time sectionaccording to the compensation method for each time section. For example,when the wireless communication terminal apply the 0-degree or180-degree phase shift to the L-SIG to generate the RL-SIG, the wirelesscommunication terminal multiplies a value selected by 1-bit informationof +1 or −1 by each time section of an L-SIG signal. At this time, thewireless communication terminal receiving the signal may multiply eachtime section by +1 to compensate the signal, and then compare thecompensated signal with the signal of the corresponding time section ofthe L-SIG signal. In addition, the wireless communication terminalreceiving the signal may multiply each time section by −1 to compensatethe signal, and then compare the compensated signal with the signal ofthe corresponding time section of the L-SIG signal.

When the wireless communication terminal determines that the receivedsignal is RL-SIG, the wireless communication terminal obtains signalinginformation of the RL-SIG based on the signal compensation. At thistime, the wireless communication terminal may obtain the signalinginformation of the RL-SIG based on at least one of a magnitude change ofa time section specific signal and a phase shift of a signal.Specifically, the wireless communication terminal may obtain thesignaling information of the RL-SIG based on a value used for timesection specific signal compensation. In a specific embodiment, thewireless communication terminal may obtain the signaling information ofthe RL-SIG based on a signal magnitude used for time section specificsignal compensation. For example, the signal magnitude used for sectionspecific signal compensation may indicate the value of the signalinginformation of the RL-SIG. In another specific embodiment, the wirelesscommunication terminal may obtain the signaling information of theRL-SIG based on a phase shift value of a signal used for time sectionspecific signal compensation. For example, the phase shift value of thesignal used for section specific signal compensation may indicate thevalue of the signaling information of the RL-SIG.

FIG. 20 shows an RL-SIG for transmitting information through a differentmodulation method different than L-SIG according to an embodiment of thepresent invention.

The wireless communication terminal may signal information through theRL-SIG modulation method. Specifically, the wireless communicationterminal may modulate the RL-SIG using a different modulation methodthan a modulation method of the L-SIG.

However, it is not desirable for the wireless communication terminal totransmit RL-SIG with QBPSK to avoid confusion with VHT-SIG or HT-SIG. Inaddition, the wireless communication terminal may generate the RL-SIG byshifting the phase of the L-SIG signal modulated with BPSK. At thistime, the wireless communication terminal may shift the phase of theL-SIG signal to distinguish the RL-SIG generated by shifting the phasefrom the QBPSK modulated signal. For example, the wireless communicationterminal may shift the phase of the L-SIG signal by an angle other than180 degrees. Since the phase of a signal modulated with BPSK and QBPSKhas a difference of 90 degrees or 270 degrees as shown in FIG. 20(a), ifthe phase of the L-SIG signal modulated with BPSK is shifted by 90degrees or 270 degrees, this is because the signal has the same formatas the signal modulated with QBPSK. Therefore, the wirelesscommunication terminal may generate the RL-SIG by shifting the phase ofthe L-SIG signal by 45 degrees or 135 degrees as shown in FIGS. 18(b),18(c), and 18(d).

The 11a physical layer frame is modulated through any one method ofBPSK/QPSK/16 QAM/64 QAM. Therefore, the wireless communication terminalmay use four kinds of constellation points during RL-SIG modulation. Forexample, when 16 QAM is selected as shown in FIG. 18(d), if the RL-SIGis configured through the corresponding constellation point, theinformation may be transmitted through the corresponding constellationselection. In other words, up to 2-bit information may be transmittedaccording to a specific constellation selection among BPSK/QPSK/16QAM/64 QAM. Alternatively, the phase or magnitude of the signalcorresponding to at least one of the four kinds of constellation pointsmay be selected in advance and used as additional informationtransmission.

The wireless communication terminal may modulate the RL-SIG signal andthe signal including the non-legacy signaling field after the RL-SIGthrough the same manner. Through this, the wireless communicationterminal may prevent confusion between the non-legacy physical layerframe and the 11ac physical layer frame.

In another specific embodiment, the RL-SIG may be modulated with BPSKand the non-legacy signaling field after RL-SIG may be modulated withQPSK. In such a case, the wireless communication terminal may increasethe information capacity of the non-legacy signaling field and preventconfusion between the non-legacy physical layer frame and the 11acphysical layer frame.

The wireless communication terminal may generate an RL-SIG by adding asubcarrier to the L-SIG signal. The subcarriers further transmitted inthe RL-SIG signal are referred to as additional subcarriers. At thistime, the wireless communication terminal may signal information throughadditional subcarriers. This will be described with reference to FIG.21.

FIG. 21 shows an RL-SIG generated by adding a subcarrier to an L-SIGaccording to an embodiment of the present invention.

The wireless communication terminal uses a subcarrier whose index valuecorresponds to −26 to 26 to transmit the L-SIG signal. The wirelesscommunication terminal may transmit subcarriers corresponding to indexvalues other than −26 to 26 as an additional subcarrier. Specifically,the wireless communication terminal may transmit a subcarrier having anindex value equal to at least one of −28, −27, 27, and 28 as anadditional subcarrier.

In a specific embodiment, the wireless communication terminal may signalinformation through at least one of the magnitude and phase of thesignal transmitted by the additional subcarrier.

In addition, the wireless communication terminal may determine anon-legacy physical layer frame based on an additional subcarrier. Forexample, when the first symbol transmitted after the L-SIG of thereceived signal is modulated with BPSK and the subcarrier having anindex value of 27 is transmitted, the wireless communication terminalmay determine that the received signal is a non-legacy physical layerframe.

Further, the additional subcarriers may be utilized to interpret theinformation signaled by the remaining subcarriers transmitting theRL-SIG signal. Specifically, additional subcarriers may indicate whetherthe RL-SIG signal signals additional information. For example, it mayindicate whether to transmit additional information to the RL-SIG basedon the information transmitted through the additional subcarrier.Further, the additional subcarrier may indicate whether the RL-SIGsignal is generated by shifting the phase of the L-SIG signal. Further,the additional subcarrier may indicate whether the RL-SIG signal isgenerated by changing the magnitude of the L-SIG signal. Further, theadditional subcarrier may indicate whether the RL-SIG signal isgenerated by changing the modulation method of the L-SIG signal.

Further, the additional subcarrier may indicate the size or unit of thefrequency section when the RL-SIG signal divides the L-SIG signal byeach frequency section and modifies the signal by each frequencysection.

In the embodiment of FIG. 21, the positions and the number of pilotsubcarriers are the same as the positions and numbers of pilotsubcarriers in the L-SIG signal. However, the positions and the numberof pilot subcarriers of the RL-SIG signal are not limited thereto. Aspecific embodiment of the pilot subcarrier of the RL-SIG signal will bedescribed in detail with reference to FIG. 22.

FIG. 22 shows that RL-SIG signals information through a pilot subcarrieraccording to an embodiment of the present invention.

The wireless communication terminal may signal information through theRL-SIG modulation method. Specifically, the wireless communicationterminal may signal information through at least one of the size, phaseshift, and location of the pilot subcarrier of the RL-SIG. At this time,the information may be additional information or information indicatingthat the signal is RL-SIG.

In two consecutive OFDM symbols, it is normal that the channel change isnot severe. Therefore, when the wireless communication terminal receivethe RL-SIG signal, the wireless communication terminal may performdemodulation using the pilot subcarriers included in the L-SIG signal.In consideration of this, during the RL-SIG transmission, the wirelesscommunication terminal may transmit a smaller number of pilotsubcarriers than the number of pilot subcarriers of the L-SIG in theRL-SIG signal. Also, the wireless communication terminal may nottransmit the pilot subcarrier in the RL-SIG. Therefore, the wirelesscommunication terminal may transmit a subcarrier for transmittingsignaling information to the pilot subcarrier location of the L-SIG.

Also, the location of the data subcarrier of the RL-SIG signal may bedifferent from the location of the data subcarrier of the L-SIG signal.At this time, the location of the pilot subcarrier of the RL-SIG signalmay be different from the location of the pilot subcarrier of the L-SIGsignal. For example, in the RL-SIG signal, the four pilot subcarriersmay be located at both ends of the frequency band, and the datasubcarriers may be used to the locations of the pilot subcarriers in theL-SIG signal.

Also, the wireless communication terminal may signal information througha modulation pattern or sequence of pilot subcarriers of the RL-SIG. Atthis time, the wireless communication terminal receiving the RL-SIGsignal may obtain information through correlation characteristics (e.g.correlation) based on the specific pattern or transition stateinformation whose size, phase, etc. applied to the pilot subcarrier isvaried. As described above, the information may be additionalinformation or information indicating that the signal is RL-SIG.

In addition, the wireless communication terminal may signal informationthrough at least one of a method of mapping RL-SIG data to a subcarrierand a method of mapping a pilot signal to a subcarrier. Specifically,the wireless communication terminal may specify an index of a subcarrierof RL-SIG by applying an offset to an index mapping of an L-SIGsubcarrier. At this time, the wireless communication terminal may signalinformation through an offset value. For example, the wirelesscommunication terminal may transmit data, which is transmitted throughthe first subcarrier transmitting the L-SIG, through the thirdsubcarrier of the RL-SIG. At this time, the offset value of thesubcarrier mapping may indicate additional information. In anotherspecific embodiment, the wireless communication terminal may specify anindex of a subcarrier of RL-SIG by shifting the index of the subcarrierof L-SIG. At this time, the wireless communication terminal may signalinformation through a shift value. In another specific embodiment, thewireless communication terminal may designate an index of a subcarrierof RL-SIG by performing a mod operation on the index value of thesubcarrier of L-SIG. In a specific embodiment, the wirelesscommunication terminal may add an offset to the index of the subcarrierof the L-SIG, and divide the sum value by the designated number to mapthe data to the index of the subcarrier of the RL-SIG corresponding tothe remaining value. For example, the wireless communication terminalmay add an offset value to the subcarrier index of the L-SIG, and mapthe data to the index of the subcarrier of RL-SIG corresponding to theremainder value obtained by dividing the value obtained by adding theoffset by 26. The subcarrier index of the RL-SIG applying an offset whenthe wireless communication terminal maps subcarriers may be appliedusing at least one of data and subcarriers for pilot transmission. Inaddition, the wireless communication terminal may apply an offset whenmapping not only the subcarriers corresponding to indexes −26 to 26 butalso the subcarriers to be transmitted in addition to the indexes −26 to26.

In addition, the wireless communication terminal may again transmit,through the RL-SIG, only a portion of information included in L-SIG. Atthis time, the wireless communication terminal may transmit additionalinformation through the remaining fields of the RL-SIG other than thefields for the partial information of the L-SIG.

Through FIGS. 15 to 22, the method in which the wireless communicationterminal signals information other than auto detection through theRL-SIG has been described. At this time, specific information that maybe signaled includes a new transmission mode of a physical layer frame,information for symbol configuration, information on the structure of aphysical layer frame, information for performing CCA, information fordecoding a non-legacy signaling field, and information for a wirelesscommunication terminal belonging to another BSS.

Specifically, the new transmission mode of the physical layer frame mayinclude a transmission mode for long range transmission. In a specificembodiment, the transmission mode for long range transmission mayindicate that a new structure of physical layer frame for long rangetransmission is used. In addition, the information for symbolconfiguration may include at least one of OFDM symbol synchronization,FFT size, and CP length. In addition, the information on the structureof the physical layer frame may include at least one of the number oftransmission symbols of the STF/LTF, the transmission order, the type ofthe signaling field, the length of the signaling field, and the methodof interpreting the signaling field. In addition, the information forperforming the CCA may include at least one of BSS color, BSS colorapplication, and offset value for the threshold value in the SD/ED to beused during CCA.

The information for decoding the non-legacy signaling field mayspecifically be information for decoding the TXOP duration indicated bythe non-legacy signaling field. Specifically, the information fordecoding the non-legacy signaling field may be the granularity of theTXOP duration indicated by the non-legacy signaling field. In yetanother specific embodiment, the information for decoding the non-legacysignaling field may be an offset value of the TXOP duration indicated bythe non-legacy signaling field.

The information for the wireless communication terminal belonging toanother BSS may be information indicating the relative position of thefrequency band in which the RL-SIG is transmitted. At this time, therelative position may indicate that the frequency band is high or low.Also, when the 80 MHz+80 MHz frequency band is used, the relativeposition may indicate either the relatively high frequency band of 80MHz or the relatively low frequency band of 80 MHz.

A wireless communication terminal belonging to another BSS may have todecode the value of the non-legacy signaling field in order to performSpatial Reuse (SR). At this time, the wireless communication terminalbelonging to another BSS may not know the relative position of thefrequency band in which the signal is transmitted, so that when thenon-legacy signaling field indicates information for a plurality offrequency bands, the wireless communication terminal belonging toanother BSS may not determine which frequency band corresponding to avalue of a non-legacy signaling field should be obtained. Accordingly,the wireless communication terminal may transmit information indicatingthe relative position of the frequency band in which the RL-SIG istransmitted through the RL-SIG. At this time, the wireless communicationterminal belonging to another BSS may determine the relative position ofthe frequency band in which the RL-SIG is transmitted based on theRL-SIG. The wireless communication terminal belonging to another BSS maydecode a non-legacy signaling field based on its relative location. Forexample, the wireless communication terminal belonging to another BSSmay decode information on Spatial Reuse (SR) indicated by a non-legacysignaling field based on a relative location.

As described above, when the legacy wireless communication terminal maynot know the duration of the non-legacy physical layer frame, theoperation efficiency of the legacy wireless communication terminal maybe low and a transmission collision may occur between the legacywireless communication terminal and the non-legacy wirelesscommunication terminal. Specifically, when a non-legacy physical layerframe is transmitted, the legacy wireless communication terminal may notknow the duration of the non-legacy physical layer frame and may performchannel sensing repeatedly. Also, if the legacy wireless communicationterminal does not repeatedly perform channel sensing, when a non-legacyphysical layer frame is transmitted, a legacy wireless communicationterminal may attempt transmission and a transmission collision with anon-legacy wireless communication terminal may occur.

To solve this problem, the L-SIG may include length information used fordetermining the duration of a non-legacy physical layer frame after theL-SIG. For convenience of explanation, the length information isreferred to as L_LENGTH.

A method of setting L_LENGTH by the legacy wireless communicationterminal and a method of obtaining the duration of the non-legacyphysical layer frame according to the L_LENGTH length by the legacywireless communication terminal will be described with reference toFIGS. 23 to 17.

FIG. 23 shows an equation for obtaining a transmission time of anon-legacy physical layer frame by a wireless communication terminalaccording to an embodiment of the present invention.

The transmission time TXTIME of the non-legacy physical layer frame isthe sum of the duration of a legacy preamble T_(L) _(_) _(PREAMBLE), theduration of a non-legacy preamble T_(HE) _(_) _(PREAMBLE), the dataduration of a non-legacy physical layer frame T_(HE) _(_) _(DATA), andthe packet extension duration of a non-legacy physical layer frameT_(PE). At this time, the duration of the legacy preamble T_(L) _(_)_(PREAMBLE) indicates the duration to the legacy signaling field in theduration of the non-legacy physical layer frame. Also, a packetextension indicates a padding added after a Frame Check Sequence (FCS)field of a non-legacy physical layer frame or Forward Error Correction(FEC).

The data duration T_(HE) _(_) _(DATA) of the non-legacy physical layerframe is the product of the symbol duration T_(HE) _(_) _(SYMBOL) of thenon-legacy physical layer frame and the number N_SYM of symbols of dataof the non-legacy physical layer frame. The symbol duration T_(HE) _(_)_(SYMBOL) of the non-legacy physical layer frame is a value obtained byadding guard interval duration T_(GI) to a signal of 12.8 us lengthincluding data excluding the symbol's guard interval cyclic prefix.

FIG. 24 shows an equation for obtaining length information included inL-SIG by a wireless communication terminal according to an embodiment ofthe present invention.

The legacy wireless communication terminal determines that L_LENGTH islength information included in signaling of the legacy physical layerframe, and indicates the size of data included in the legacy physicallayer frame. In wireless communication, data is transmitted by a symbolunit. Also, the duration of a symbol of a non-legacy physical layerframe is different from the duration of a symbol of a legacy physicallayer frame. Therefore, the non-legacy wireless communication terminalsets L_LENGTH based on the duration of the symbol of the legacy physicallayer frame.

Specifically, the non-legacy wireless communication terminal may setL_LENGTH based on a value obtained by dividing the duration TXTIME—T_(L)_(_) _(PREAMBLE) of the non-legacy physical layer frame after the L-SIGby the duration aSymbolLength of the symbol of the legacy physical layerframe. Also, as described above, in wireless communication, data istransmitted by a symbol unit, and a legacy wireless communicationterminal converts the size of data represented by L_LENGTH into a symbolunit of a legacy physical layer frame to determine the duration of aphysical layer frame. Therefore, the non-legacy wireless communicationterminal divides the duration of the non-legacy physical layer frameafter the L-SIG by the duration aSymbolLength of the legacy physicallayer frame symbol and sets L_LENGTH based on the ceiling calculatedvalue 2401.

Therefore, the non-legacy wireless communication terminal sets L_LENGTHbased on the duration of the symbol of the legacy physical layer frame.Specifically, the non-legacy wireless communication terminal may setL_LENGTH based on the number of Octets N_(OPS) transmittable per symbolof the legacy physical layer frame. Accordingly, the wirelesscommunication terminal may perform a ceiling operation 2401 on a valueobtained by dividing the duration TXTIME—T_(L) _(_) _(PREAMBLE) of thelegacy physical layer frame symbol after L-SIG by the durationaSymbolLength of the legacy physical layer frame symbol, and setL_Length based on the value obtained by multiplying the number of OctetsN_(OPS) transmittable per symbol of the legacy physical layer frame.

Since the concrete value of the legacy preamble included in thenon-legacy physical layer frame is fixed, the wireless communicationterminal may apply the following concrete values to calculate L_LENGTH.The L-STF length is 8 us, the L-LTF length is 8 us, and the L-SIG lengthis 4 us. Therefore, the duration TXTIME—T_(L) _(_) _(PREAMBLE) of thenon-legacy physical layer frame after the L-SIG is a value obtained bysubtracting 20 us from the duration of the non-legacy physical layerframe. Also, the duration aSymbolLength of the legacy physical layerframe symbol is 4 us/symbol. When L_DATARATE is 6 Mbps, the number ofOctets N_(OPS) transmittable to one symbol with a duration of 4 us is 3.

The legacy physical layer frame is located after the field indicatingthe length information and includes an additional field not included inthe length indicated by the length information of the legacy physicallayer frame. Therefore, the non-legacy wireless communication terminalmay set L_LENGTH based on the structure of the legacy physical layerframe.

Specifically, the non-legacy wireless communication terminal must setL_LENGTH based on the length of the legacy PLCP service field and thelength of one PLCP tail field. Specifically, when the non-legacywireless communication terminal set L_LENGTH, the non-legacy wirelesscommunication terminal should subtract the value based on the sum of thelength of the PLCP service field and the length of one PLCP tail field.The legacy physical layer frame further includes a PLCP service fieldand a PLCP tail field in addition to a preamble corresponding to alegacy preamble of a non-legacy physical layer frame and data. PLCPservice field length and PLCP tail field length are in bit units, andL_LENGTH is displayed in byte units, in order to set L_LENGTH, thenon-legacy wireless communication terminal divides the length of thePLCP service field and the length of the PLCP tail field by 8 andperforms the ceiling operation 2402.

The length of the PLCP service field and the length of the PLCP tailfield are fixed. Therefore, in order to set L_LENGTH, the non-legacywireless communication terminal may divide the length of the PLCPservice field and the length of the PLCP tail field by 8 and apply 3 tothe rounded value.

Therefore, the non-legacy wireless communication terminal may set thevalue of L_LENGTH through the equation of FIG. 24.

FIG. 25 shows a method of a wireless communication terminal to determinewhether the existence of a packet extension is unclear according to anembodiment of the present invention.

If the non-legacy physical layer frame includes the above-mentionedpacket extension and the length of the packet extension satisfies acertain condition, a wireless communication terminal receiving anon-legacy physical layer frame may be confused whether the signaltransmitting the non-legacy physical layer frame is a symbol of data ora padding according to a packet extension. In particular, when awireless communication terminal transmits a non-legacy physical layerframe to a plurality of wireless communication terminals through OFDMA,a wireless communication terminal receiving a non-legacy physical layerframe may be confused whether the signal transmitting the non-legacyphysical layer frame is a symbol of data or a padding according to apacket extension.

When the wireless communication terminal receiving the non-legacyphysical layer frame is confused in such a way, the wirelesscommunication terminal may signal disambiguate information thatdisambiguate the ambiguity on whether packet extensions of non-legacyphysical layer frames are included. At this time, the information thatdisambiguates ambiguity on whether or not the packet extension of thenon-legacy physical layer frame is included may be included in thenon-legacy signaling field of the non-legacy physical layer frame. Forconvenience of description, information that disambiguates ambiguity onwhether a packet extension is included is referred to as aPE-Disambiguity field.

The non-legacy wireless communication terminal may set thePE-Disambiguity field based on the duration T_(SYM) of the symbol of thenon-legacy physical layer frame and the increment of duration to set thevalue of L_LENGTH based on the duration aSymbolLength of the symbol ofthe legacy physical layer frame.

Specifically, in relation to the non-legacy wireless communicationterminal, the increment of duration to set the value of L_LENGTH basedon the symbol duration aSymbolLength of the symbol of the legacyphysical layer frame is a value obtained by multiplying a difference2501 between a value obtained by performing a ceiling operation on avalue obtained by dividing the duration of the non-legacy physical layerframe after the L-SIG by the duration aSymbolLength of the legacyphysical layer frame symbol and a value before the ceiling operation bythe duration aSymbolLength of the legacy physical layer frame.

If the sum of the increment of duration to set the value of L_LENGTHbased on the duration aSymbolLength of the symbol of the legacy physicallayer frame and the duration of the packet extension is identical to orgreater than the duration T_(SYM) of the symbol of the non-legacyphysical layer frame, the non-legacy wireless communication terminal maysignal information on the packet extension. This is because the sum ofthe increment of duration to set the value of L_LENGTH based on theduration aSymbolLength of the symbol of the legacy physical layer frameand the duration of the packet extension indicates the duration of awireless signal not including real data.

As a result, when the equation of FIG. 25 is satisfied, in relation tothe non-legacy wireless communication terminal, PE-Disambiguitydisambiguates ambiguity on whether the non-legacy physical layer framesincludes the packet extension. For example, when the equation of FIG. 25is satisfied, the non-legacy wireless communication terminal may set thePE-Disambiguity to 1. In addition, when the equation of FIG. 25 is notsatisfied, the non-legacy wireless communication terminal may set thePE-Disambiguity to 0.

Also, as described above, the duration aSymbolLength of the legacyphysical layer frame symbol are 4 us. Therefore, 4 us may be applied tothe equation of FIG. 25.

However, there is a case that the signaling through the PE disambiguityfield is not necessary because it is clear whether the packet extensionis included or not. For example, if the GI is 0.8 us or 1.6 us and theduration T_(PE) of the packet extension is either 0, 4 us, or 8 us, itdoes not always satisfy the equation of FIG. 25. Also, if the GI is 3.2us and the duration T_(PE) of the packet extension is either 0, 4 us, 8us, and 12 us, the equation of FIG. 25 is not always satisfied. On theother hand, if the GI is 3.2 us and the duration T_(PE) of the packetextension is 16 us, the equation of FIG. 25 is always satisfied. If theduration T_(PE) of the allowed packet extensions is limited by thepacket extension capability of the wireless communication terminal, thewireless communication terminal may determine whether the PEdisambiguity field needs to be set through the GI value.

Therefore, the non-legacy wireless communication terminal may signalother information through the PE disambiguity field. In a specificembodiment, the non-legacy wireless communication terminal may signalCRC information for the signaling field through the PE disambiguityfield.

FIG. 26 shows a method of determining the length of a packet extensionby a wireless communication terminal according to an embodiment of thepresent invention.

The wireless communication terminal receiving the non-legacy physicallayer frame may obtain the number of symbols N_(SYM) including databased on the value of the L_LENGTH field and the value b_(PE) _(_)_(Disambiguity) of the PE disambiguity field. Specifically, the wirelesscommunication terminal obtains the duration of a symbol of data based onthe L_LENGTH field. For this, the wireless communication terminalobtains the duration of the non-legacy physical layer frame except thelegacy preamble by adding 3, which is the value 2602 obtained byconverting the lengths of the PLCP service field and PLCP tail fieldinto bytes, to L_LENGTH, then dividing it by three bytes, which the datasize 2603 transmittable by one symbol transmitting a legacy physicallayer frame, and multiplying it by 4 us, which is the duration of thesymbol of the legacy physical layer frame. The wireless communicationterminal subtracts 2601 the duration T_(HE-PREAMBLE) of the non-legacypreamble from the duration of the non-legacy physical layer frameexcluding the obtained legacy preamble, and performs a flooringoperation on a value obtained by dividing it by the duration T_(SYM) ofthe symbol of the non-legacy physical layer frame. The wirelesscommunication terminal obtains the number of symbols N_(SYM) includingthe data by subtracting the value b_(PE) _(_) _(Disambiguity) of the PEdisambiguity field from the value obtained through the flooringoperation value.

The wireless communication terminal obtains the duration T_(PE) of thepacket extension based on the number of symbols N_(SYM) including thedata and the value of L_LENGTH. Specifically, the wireless communicationterminal subtracts the duration N_(SYM)×T_(SYM) of the symbol of thedata from the value 2601 obtained by subtracting the durationT_(HE-PREAMBLE) of the non-legacy preamble from the duration of thenon-legacy physical layer frame excluding the legacy preamble, and thendivide it by 4 us, which is the duration of the symbol of the legacyphysical layer frame. At this time, the value acquired by the wirelesscommunication terminal includes an additional time for adjusting thevalue to the duration value of the symbol of the legacy physical layerframe. Therefore, the wireless communication terminal applies theflooring operation to the obtained value, and again multiplies theflooring value by 4 us, which is the duration of the symbol of thelegacy physical layer frame, to obtain the duration T_(PE) of the packetextension.

FIG. 27 shows that a legacy wireless communication terminal obtains theduration of a non-legacy physical layer frame based on L_LENGTHaccording to an embodiment of the present invention.

The legacy wireless communication terminal obtains the duration RXTIMEof the non-legacy physical layer frame based on L_LENGTH. Specifically,the legacy wireless communication terminal may access the wirelessmedium based on the obtained duration of the non-legacy physical layerframe.

Specifically, the legacy wireless communication terminal may obtain theduration RXTIME of the non-legacy physical layer frame based onL_LENGTH, the length of the PLCP service fields, and the length of onePLCP tail field. Specifically, L_LENTH may be converted into the numberof non-legacy symbols based on the size N_(OPS) of data that one symbolof the legacy physical layer frame may transmit. At this time, the sizeN_(OPS) of the data transmittable by one symbol of the legacy physicallayer frame is expressed in units of Octets (bytes). In addition, thelegacy wireless communication terminal converts the length of the PLCPservice field and the length of one PLCP tail field into byte units. Thelegacy wireless communication terminal divides the length of the PLCPservice field and the length of one PLCP tail field, which are convertedin byte units, by the size N_(OPS) of data transmittable by one symbolof the legacy physical layer frame to convert the length of the PLCPservice field and the length of one PLCP tail field into symbol units.The legacy wireless communication terminal performs a ceiling operationon L_LENGTH and the length of the PLCP service fields and the length ofone PLCP tail field, which are converted in symbol units. As describedabove, wireless communication is performed in symbol units.

The legacy wireless communication terminal obtains the duration of thenon-legacy physical layer frame by multiplying the ceiling operationvalue by the duration aSymbolLength of the symbol of the legacy physicallayer frame and adding the duration T_(L) _(_) _(PREAMBLE) of thepreamble of the legacy physical layer frame.

As described above, the length of the PLCP service field and the lengthof one PLCP tail field are converted into byte units, and its ceilingoperation value is 3. Also, the number of bytes N_(OPS) transmittable byone symbol of the legacy physical layer frame is 3. Also, the durationaSymbolLength of the symbol of the legacy physical layer frame symbol is4 us. Since the L-STF length is 8 us, the L-LTF length is 8 us, and theL-SIG length is 4 us, the duration T_(L) _(_) _(PREAMBLE) of thepreamble of the legacy physical layer frame is 20 us.

Therefore, by applying this value, the equation of FIG. 27 may beobtained, and the legacy wireless communication terminal may obtain theduration RXTIME of the non-legacy physical layer frame according to theequation of FIG. 27.

As described above, the legacy wireless communication terminal transmitsdata in symbol units of a legacy physical layer frame. Also, when thelegacy wireless communication terminal obtains the duration of thenon-legacy physical layer frame based on the L_LENGTH, the legacywireless communication terminal performs a ceiling operation based onthe value obtained by dividing the size of data transmittable by onesymbol of the legacy physical layer frame. Thus, the legacy wirelesscommunication terminal may process L_LENGTH having different lengths asthe duration of a non-legacy physical layer frame of the same size. Atthis time, the range of the L_LENGTH, which is regarded as the durationof non-legacy physical layer frames of the same size, is determinedaccording to the data size the size of data transmittable by one symboltransmitting a legacy physical layer frame. For example, it is assumedthat a data size that one symbol of a legacy physical layer frame maytransmit is 3 bytes. At this time, the legacy wireless communicationterminal acquires the duration RXTIME of the same non-legacy physicallayer frame even if the value of the L_LENGTH changes from 31 to 32 or33. With this feature, the non-legacy physical wireless communicationterminal may signal information other than the duration of thenon-legacy physical layer frame with the value of the L_LENGTH.

In a specific embodiment, through the remaining value when the L_LENGTHis divided by the size of data transmittable by one symbol of the legacyphysical layer frame, the non-legacy physical wireless communicationterminal may signal information other than the duration of a non-legacyphysical layer frame. As described above, the size of data that onesymbol of a legacy physical layer frame may transmit is 3 bytes.Furthermore, the L_LENGTH field indicates the length in byte units.Therefore, the non-legacy physical wireless communication terminal maysignal information other than the duration of the non-legacy physicallayer frame through the remainder when the L_LENGTH is divided by 3.

When using this signaling method, the modification in the signalinginformation does not affect the operation of the legacy wirelesscommunication terminal. Also, through this signaling method, thenon-legacy wireless communication terminal may transmit additionalinformation without using additional transmission resources.

Information other than the duration of the non-legacy physical layerframe may be in the format of a non-legacy signaling field. At thistime, the format of the non-legacy signaling field may indicate whetheror not a specific field is included. For example, the format of thenon-legacy signaling field may include whether or not the HE-SIG-B fieldis included. In yet another specific embodiment, the format of thenon-legacy signaling field may be whether HE-SIG-A is repeated.

Also, the non-legacy wireless communication terminal may signal theformat of the non-legacy signaling field by combining the L_LENGTH valuewith the modulation method of the symbol transmitting the HE-SIG-A.Specifically, the modulation method of the first symbol transmittingHE-SIG-A is BPSK. This is for auto detection of non-legacy wirelesscommunication terminals as described above. Therefore, the wirelesscommunication terminal may signal the format of the non-legacy signalingfield through the modulation method of the second symbol transmittingHE-SIG-A. Specifically, the wireless communication terminal may modulatethe second symbol transmitting HE-SIG-A with QBPSK or BPSK.

As described above, through the remaining value when the L_LENGTH isdivided by the size of data transmittable by one symbol of the legacyphysical layer frame, the non-legacy wireless communication terminal maysignal information other than the duration of a non-legacy physicallayer frame. For this, when the non-legacy wireless communicationterminal sets the length of the L_LENGTH, the non-legacy wirelesscommunication terminal should add or subtract a positive integer lessthan the size of data transmittable by zof the legacy physical layerframe in the length set based on the duration of the non-legacy physicallayer frame. This will be described with reference to FIGS. 28 to 31.

FIG. 28 shows that a wireless communication terminal according to anembodiment of the present invention adds a predetermined range ofintegers to the format of a non-legacy signaling field while settingL_LENGTH.

As described with reference to FIG. 24, the non-legacy wirelesscommunication terminal may set the L_LENGTH based on the duration of thenon-legacy physical layer frame. In order to signal information otherthan the duration of the non-legacy physical layer frame through theL_LENGTH, the non-legacy wireless communication terminal may add apositive integer m smaller than the size of data transmittable by onesymbol of the legacy physical layer frame in the length set based on theduration of the non-legacy physical layer frame. For convenience ofexplanation, a positive integer smaller than the size of datatransmittable by one symbol of the legacy physical layer frame isreferred to as m. Specifically, when the data rate of the legacyphysical layer frame is 6 Mbps, the size of data that one symbol of thelegacy physical layer frame may transmit is 3 bytes. Thus, m may be 1 or2. Therefore, the non-legacy wireless communication terminal may add 1or 2 to the length set based on the duration of the non-legacy physicallayer frame.

At this time, the value of m may represent information other than theduration of the non-legacy physical layer frame as described above.

The non-legacy wireless communication terminal receiving the non-legacyphysical layer frame may obtain information other than the duration ofthe non-legacy physical layer frame based on the L_LENGTH. Specifically,the non-legacy wireless communication terminal may divide the value ofthe L_LENGTH by the size of data transmittable by one symbol of thelegacy physical layer frame to obtain a value of m, i.e., the remaining,and may obtain information other than the duration of the frame based onthe value of m.

As described with FIG. 27, since the legacy wireless communicationterminal performs a ceiling operation on a value obtained by dividingthe size of data transmittable by one symbol of the legacy physicallayer frame, even if the value of m changes, the legacy wirelesscommunication terminal obtains the duration of the legacy physical layerframe. Therefore, the wireless communication terminal may set the valueof the L-LENGTH through the equation of FIG. 28, and signal informationother than the duration of the non-legacy physical layer frame throughthe value of m.

FIG. 29 shows a method for determining the length of a packet extensionby a wireless communication terminal according to an embodiment of thepresent invention when adding a predetermined integer according to theformat of a non-legacy signaling field while setting L_LENGTH.

As described with reference to FIG. 26, the wireless communicationterminal receiving the non-legacy physical layer frame may obtain thenumber of symbols N_(SYM) including data based on the value of theL_LENGTH field and the value b_(PE) _(_) _(Disambiguity) of the PEdisambiguity field. In addition, the non-legacy wireless communicationterminal receiving the non-legacy physical layer frame may obtain theduration T_(PE) of the packet extension based on the L_LENGTH and thenumber of symbols N_(SYM) including data.

As shown in FIG. 28, m may be added to signal information other than theduration of the non-legacy physical layer frame through the length ofthe L_LENGTH.

In such a case, since the L_LENGTH includes a value for signalinginformation other than the duration of the non-legacy physical layerframe, the wireless communication terminal receiving the non-legacyphysical layer frame must obtain, in consideration of m, the number ofsymbols N_(SYM) including the data and the duration T_(PE) of the packetextension.

Thus, a non-legacy wireless communication terminal receiving anon-legacy physical layer frame obtains the value of m by using theremaining obtained by dividing the L-LENGTH by the size of datatransmittable by one symbol of the legacy physical layer frame, andobtains the number of symbols N_(SYM) including data based on a valueobtained by subtracting the value of m from the value of the L-LENGTH.

In addition, the non-legacy wireless communication terminal receivingthe non-legacy physical layer frame may obtain the duration T_(PE) ofthe packet extension based on the value obtained by subtracting thevalue of m from the value of the L_LENGTH.

Through the embodiments of FIGS. 28 and 29, a method has been describedin which a wireless communication terminal signals information otherthan the duration of a non-legacy physical layer frame through theL_LENGTH by adding the value of m when the L-LENGTH is set. However, insuch a case, the duration of the non-legacy physical layer frameobtained by the legacy wireless communication terminal is longer by onesymbol of the legacy physical layer frame compared to a case thatinformation other than the duration of the non-legacy physical layerframe is not signaled through the L-LENGTH. This is because the legacywireless communication terminal obtains the duration of the non-legacyphysical layer frame based on the ceiling operation as described withreference to FIG. 27.

Therefore, according to the embodiments of FIGS. 28 and 29, signalinginformation other than the duration of the non-legacy physical layerframe through the L-LENGTH affects the operation of the legacy wirelesscommunication terminal. As a result, legacy wireless communicationterminals suffer losses in the competition procedure for transmission. Amethod for signaling information other than the duration of thenon-legacy physical layer frame using the L_LENGTH to solve this problemwill be described with reference to FIGS. 30 and 31.

FIG. 30 shows that a wireless communication terminal according to anembodiment of the present invention subtracts a predetermined integeraccording to the format of a non-legacy signaling field while settingL_LENGTH.

As described with reference to FIG. 24, the non-legacy wirelesscommunication terminal may set the L_LENGTH based on the duration of thenon-legacy physical layer frame. In order to signal information otherthan the duration of the non-legacy physical layer frame through theL_LENGTH, the non-legacy wireless communication terminal may subtract apositive integer m smaller than the size of data transmittable by onesymbol of the legacy physical layer frame in the length set based on theduration of the non-legacy physical layer frame. For convenience ofexplanation, a positive integer smaller than the size of datatransmittable by one symbol of the legacy physical layer frame isreferred to as m. Specifically, when the data rate of the legacyphysical layer frame is 6 Mbps, the size of data that one symbol of thelegacy physical layer frame may transmit is 3 bytes. Thus, m may be 1 or2. Therefore, the non-legacy wireless communication terminal maysubtract 1 or 2 from the length set based on the duration of thenon-legacy physical layer frame.

At this time, m may represent information other than the duration of thenon-legacy physical layer frame as described above. In other words, avalue obtained by subtracting m from the size of data transmittable byone symbol of the legacy physical layer frame may represent informationother than the duration of the non-legacy physical layer frame asdescribed above.

As described with reference to FIG. 28 above, the non-legacy wirelesscommunication terminal receiving the non-legacy physical layer frame mayobtain information other than the duration of the non-legacy physicallayer frame based on the L_LENGTH. Specifically, the non-legacy wirelesscommunication terminal obtains the remaining when the value of theL_LENGTH is divided by the size of data transmittable by one symbol ofthe legacy physical layer frame by a value obtained by subtracting mfrom the size of data transmittable by one symbol of the legacy physicallayer frame, and may obtain information other than the duration of thenon-legacy physical layer frame based on the remaining value (the valueobtained by subtracting m from the size of data that one symbol of thelegacy physical layer frame may transmit).

As described with reference to FIG. 27, the legacy wirelesscommunication terminal performs a ceiling operation on a value obtainedby dividing the size of data that one symbol of a legacy physical layerframe may transmit. Also, the value of m is smaller than the data sizeof data transmittable by one symbol of the legacy physical layer frame.Therefore, the legacy wireless communication terminal obtains theduration of the same non-legacy physical layer frame even if the valueof m changes. In addition, the duration of the non-legacy physical layerframe obtained by the legacy wireless communication terminal is the sameas the case that information other than the duration of the non-legacyphysical layer frame is not signaled through the L-LENGTH. This isbecause the legacy wireless communication terminal obtains the durationof the non-legacy physical layer frame based on the ceiling operation asdescribed with reference to FIG. 27. Thus, signaling information otherthan the duration of the non-legacy physical layer frame through theL_LENGTH by the non-legacy wireless communication terminal does notaffect the operation of the legacy wireless communication terminal.

FIG. 31 shows a method for determining the length of a packet extensionby a wireless communication terminal according to an embodiment of thepresent invention when subtracting a predetermined integer according tothe format of a non-legacy signaling field while setting L_LENGTH.

As described with reference to FIG. 26, the wireless communicationterminal receiving the non-legacy physical layer frame may obtain thenumber of symbols N_(SYM) including data based on the value of theL_LENGTH field and the value b_(PE) _(_) _(Disambiguity) of the PEdisambiguity field. In addition, the non-legacy wireless communicationterminal receiving the non-legacy physical layer frame may obtain theduration T_(PE) of the packet extension based on the L_LENGTH and thenumber of symbols N_(SYM) including data.

As shown in FIG. 30, m may be subtracted to signal information otherthan the duration of the non-legacy physical layer frame through thelength of the L_LENGTH.

In such a case, since the L_LENGTH includes a value for signalinginformation other than the duration of the non-legacy physical layerframe, the wireless communication terminal receiving the non-legacyphysical layer frame must obtain, in consideration of m, the number ofsymbols N_(SYM) including the data and the duration T_(PE) of the packetextension.

Thus, a non-legacy wireless communication terminal receiving anon-legacy physical layer frame divides LENGTH by the size of datatransmittable by one symbol of the legacy physical layer frame andsubtracts the remaining from the size of data transmittable by onesymbol of the legacy physical layer frame to obtain a value of m. Thenon-legacy wireless communication terminal may obtain the number ofsymbols N_(SYM) including data based on a value obtained by adding thevalue of m in the value of L_LENGTH.

In addition, the non-legacy wireless communication terminal receivingthe non-legacy physical layer frame may obtain the duration T_(PE) ofthe packet extension based on the value obtained by adding the value ofm in the value of L_LENGTH.

FIG. 32 shows an operation of transmitting a non-legacy physical layerframe and receiving a non-legacy physical layer frame by a wirelesscommunication terminal according to an embodiment of the presentinvention.

A first wireless communication terminal 3201 sets a legacy signalingfield (S3201). At this time, the legacy signaling field may includelength information indicating the duration of the non-legacy physicallayer frame after the legacy signaling field. At this time, the lengthinformation may be the L_LENGTH field described above. In addition, thefirst wireless communication terminal 3201 may set the value of thelength information based on the embodiment described with reference toFIGS. 23 to 31.

Specifically, the first wireless communication terminal 3201 may signalinformation other than the information indicating the duration of thenon-legacy physical layer frame through the length information. In aspecific embodiment, the first wireless communication terminal 3201 maysignal information other than information indicating the duration of anon-legacy physical layer frame through the remaining value obtained bydividing the length information by the size of data transmittable by onesymbol transmitting the legacy physical layer frame. The first wirelesscommunication terminal 3201 may set length information based on a valueobtained by subtracting the size of data transmittable by one symbol ofthe legacy physical layer frame from a value obtained by converting theduration of a non-legacy physical layer frame after the legacy signalingfield into the format of the length information and by adding theremaining value.

The first wireless communication terminal 3201 may convert the durationof the non-legacy physical layer frame after the legacy signaling fieldinto the format of the length information based on the duration of onesymbol transmitting a legacy physical layer frame and the data sizetransmitted by one symbol transmitting a legacy physical layer frame.For example, the first wireless communication terminal 3201 may setlength information according to the following equation.L_LENGTH=[(TXTIME-TL_PREAMBLE)/aSymbolLength]×N _(OPS)−[a/8]−m

L_LENGTH indicates length information. [x] represents the smallestinteger among integers greater than or equal to x. TXTIME represents theduration of a non-legacy physical layer frame. T_(L) _(_) _(PREAMBLE)indicates the duration to the legacy signaling field during the durationof the non-legacy physical layer frame. aSymbolLength represents theduration of one symbol transmitting a legacy physical layer frame.N_(OPS) represents the data size that one symbol transmitting a legacyphysical layer frame may transmit. a represents the number of bits of afield not included in the length indicated by the length informationafter the length information in the legacy physical layer frame. mrepresents a value obtained by subtracting the remaining value from thesize of data transmittable by one symbol transmitting the legacyphysical layer frame.

In addition, information other than the information indicating theduration of the non-legacy physical layer frame may indicate the formatof the non-legacy physical layer frame. Specifically, it may indicatethe format of a signaling field indicating the duration of a non-legacyphysical layer frame. In a specific embodiment, information other thaninformation indicating the duration of the non-legacy physical layerframe may indicate whether the non-legacy physical layer frame includesa predetermined field. The predetermined field may be at least one ofthe HE-SIG-B field and the repeated HE-SIG-A field described above.

The first wireless communication terminal 3201 may signal informationother than the information indicating the duration of the non-legacyphysical layer frame based on the remaining value and the modulationmethod of the third symbol after the legacy signaling field. At thistime, the first wireless communication terminal 3201 may modulate thethird symbol after the legacy signaling field with Binary Phase ShiftKeying (BPSK) or Quadrature Binary Phase Shift Keying (QBPSK).

The first wireless communication terminal 3201 transmits a non-legacyphysical layer frame including a legacy signaling field (S3203). At thistime, the first wireless communication terminal 3201 may transmit arepeated legacy signaling field generated based on the legacy signalingfield and used for auto detection, after the legacy signaling field.Specifically, the legacy signaling field may be the RL-SIG describedwith reference to FIGS. 13 to 22.

Also, the first wireless communication terminal 3201 may transmitadditional information through the repeated legacy signaling field.Specifically, the first wireless communication terminal 3201 may signaladditional information based on a modification in one or more frequencysection specific signals included in the legacy signaling field versusone or more frequency section specific signals included in the legacysignaling field. The first wireless communication terminal 3201 maysignal additional information based on a change in one or more timesection specific signals included in a repeated legacy signaling fieldversus one or more time section specific signals included in a legacysignaling field. In addition, the first wireless communication terminal3201 may signal additional information through the modulation method ofthe repeated legacy signaling field. In addition, the first wirelesscommunication terminal 3201 may transmit additional subcarriers to therepeated signaling field to signal additional information.

The first wireless communication terminal 3201 may transmit a subcarriertransmitting additional information in a location of the pilotsubcarrier of the legacy signaling field. The wireless communicationterminal may also signal additional information through a modulationpattern or sequence of pilot subcarriers in the repeated legacysignaling field. In addition, the first wireless communication terminal3201 may signal additional information through at least one of a methodof mapping data of the repeated legacy signaling field to a subcarrierand a method of mapping a pilot signal to a subcarrier.

The additional information described above may be at least one of a newtransmission mode of the physical layer frame, information for symbolconfiguration, information on the structure of the physical layer frame,and information for performing CCA. Specifically, the new transmissionmode of the physical layer frame may include a transmission mode forlong range transmission. In a specific embodiment, the transmission modefor long range transmission may indicate that a new structure ofphysical layer frame for long range transmission is used. In addition,the information for symbol configuration may include at least one ofOFDM symbol synchronization, FFT size, and CP length. In addition, theinformation on the structure of the physical layer frame may include atleast one of the number of transmission symbols of the STF/LTF, thetransmission order, the type of the signaling field, the length of thesignaling field, and the method of interpreting the signaling field. Inaddition, the information for performing the CCA may include at leastone of BSS color, BSS color application, and offset value for thethreshold value in the SD/ED to be used during CCA.

A second wireless communication terminal 3203 obtains information basedon the legacy signaling field (S3205). The second wireless communicationterminal 3203 may obtain length information indicating the duration ofthe non-legacy physical layer frame after the legacy signaling field,from the legacy signaling field and obtain information other than theinformation indicating the duration of the non-legacy physical layerframe by using the value of the length information. Specifically, thesecond wireless communication terminal 3203 may obtain information otherthan information indicating the duration of a non-legacy physical layerframe through the remaining value obtained by dividing the lengthinformation by the size of data transmittable by one symbol transmittingthe legacy physical layer frame.

Also, the second wireless communication terminal 3203 obtains the numberof symbols transmitting the non-legacy physical layer frame based on avalue obtained by adding the size of data transmittable by one symboltransmitting the legacy physical layer frame to the value of the lengthinformation and subtracting the remaining value. In a specificembodiment, the second wireless communication terminal (S3203) mayobtain the number of symbols transmitting data of a non-legacy physicallayer frame based on the equation of FIG. 31.

Also, the second wireless communication terminal 3203 obtains a durationof a packet extension included in the non-legacy physical layer framebased on a value obtained by adding the size of data transmittable byone symbol transmitting the legacy physical layer frame to the value ofthe length information and subtracting the remaining value, and thenumber of symbols transmitting the non-legacy physical layer frame.Specifically, the second wireless communication terminal 3203 may obtainthe duration of the packet extension included in the non-legacy physicallayer frame based on the equation of FIG. 31.

In addition, the second wireless communication terminal 3203 may obtaininformation other than the information indicating the duration of thenon-legacy physical layer frame based on the remaining value and themodulation method of the third symbol after the legacy signaling field.

Also, the second wireless communication terminal 3203 may obtainadditional information through the repeated legacy signaling field. Atthis time, the second wireless communication terminal 3203 may obtainadditional information based on the legacy signaling field and therepeated legacy signaling field. Specific operations of the secondwireless communication terminal 3203 may follow the embodiment describedwith reference to FIGS. 15 to 22.

Although the present invention is described by using wireless LANcommunication as an example, it is not limited thereto and may beapplied to other communication systems such as cellular communication.Additionally, while the method, device, and system of the presentinvention are described in relation to specific embodiments thereof,some or all of the components or operations of the present invention maybe implemented using a computer system having a general purpose hardwarearchitecture.

The features, structures, and effects described in the above embodimentsare included in at least one embodiment of the present invention and arenot necessary limited to one embodiment. Furthermore, features,structures, and effects shown in each embodiment may be combined ormodified in other embodiments by those skilled in the art. Therefore, itshould be interpreted that contents relating to such combination andmodification are included in the range of the present invention.

While the present invention is described mainly based on the aboveembodiments but is not limited thereto, it will be understood by thoseskilled in the art that various changes and modifications are madewithout departing from the spirit and scope of the present invention.For example, each component specifically shown in the embodiments may bemodified and implemented. It should be interpreted that differencesrelating to such modifications and application are included in the scopeof the present invention defined in the appended claims.

The invention claimed is:
 1. A wireless communication terminal thatcommunicates wirelessly, the terminal comprising: a transceiver; and aprocessor, wherein the processor is configured to receive a non-legacyphysical layer frame by using the transceiver, obtain a legacy signalingfield including information decodable by a legacy wireless communicationterminal from the non-legacy physical layer frame, obtain lengthinformation indicating information on a duration of the non-legacyphysical layer frame, from the legacy signaling field, obtaininformation other than information on the duration of the non-legacyphysical layer frame through a remaining value obtained by dividing thelength information by a data size transmittable by a symbol of a legacyphysical layer frame, wherein the data size transmittable by a symbol ofthe legacy physical layer frame is 3 octets when a data rate of thelegacy physical layer frame is 6 Mbps, and determine the number ofsymbols of data of the non-legacy physical layer frame according to afollowing equation,$N_{SYM} = {\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{{HE}\;\_\;{PREAMBLE}}} \right)/T_{SYM}} \right\rfloor - b_{{PE}\;\_\;{Disambiguity}}}$where └x┘ denotes a largest integer less than or equal to x, L_LENGTHdenotes the length information, m denotes a value obtained bysubtracting the remaining value from the data size transmittable by asymbol of the legacy physical layer frame, b_(PE) _(_) _(Disambiguity)denotes a value of PE Disambiguity field, T_(HE) _(_) _(PREAMBLE)denotes a duration of non-legacy preamble of the non-legacy physicallayer frame, T_(SYM) denotes a duration of a symbol of the data of thenon-legacy physical layer frame, wherein the PE Disambiguity field isset based on the duration of a symbol of the data of the non-legacyphysical layer frame and an increment of duration to set a value of thelength information based on a duration of a symbol of the legacyphysical layer frame.
 2. The wireless communication terminal of claim 1,wherein the processor is configured to obtain a duration of a packetextension which is a padding of the non-legacy physical layer frame,according to a following equation,$T_{PE} = {\left\lfloor \frac{\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{{HE}\;\_\;{PREAMBLE}}} \right) - {N_{SYM} \times T_{SYM}}}{4} \right\rfloor \times 4}$where └x┘ denotes a largest integer less than or equal to x, L_LENGTHdenotes the length information, m denotes the value obtained bysubtracting the remaining value from the data size transmittable by asymbol of the legacy physical layer frame, T_(HE) _(_) _(PREAMBLE)denotes the duration of non-legacy preamble of the non-legacy physicallayer frame, T_(SYM) denotes the duration of a symbol of the data of thenon-legacy physical layer frame.
 3. The wireless communication terminalof claim 1, wherein the increment of duration is a value obtained bymultiplying a difference between a value obtained by performing aceiling operation on a value obtained by dividing the duration of thenon-legacy physical layer frame after the legacy signaling field by theduration of a symbol of the legacy physical layer frame and the valueobtained by dividing the duration of the non-legacy physical layer frameafter the legacy signaling field by the duration of a symbol of thelegacy physical layer frame by the duration of a symbol of the legacyphysical layer frame.
 4. The wireless communication terminal of claim 1,wherein the processor is configured to determine a format of anon-legacy signaling field included in the non-legacy physical layerframe based on the length information.
 5. The wireless communicationterminal of claim 4, wherein the processor is configured to determinewhether the non-legacy physical layer frame comprises a predeterminedsignaling field based on the length information.
 6. The wirelesscommunication terminal of claim 1, wherein the processor is configuredto obtain the information other than the information on the duration ofthe non-legacy physical layer frame based on the remaining value and amodulation method of a third symbol after the legacy signaling field. 7.The wireless communication terminal of claim 6, wherein the modulationmethod is Binary Phase Shift Keying (BPSK) or Quadrature Binary PhaseShift Keying (QBPSK).
 8. An operation method of a wireless communicationterminal that communicates wirelessly, the method comprising: receivinga non-legacy physical layer frame by using the transceiver, obtaining alegacy signaling field including information decodable by a legacywireless communication terminal from the non-legacy physical layerframe, obtaining length information indicating information on a durationof the non-legacy physical layer frame after a legacy signaling field,from the legacy signaling field, obtaining information other than theinformation on the duration of the non-legacy physical layer framethrough a remaining value obtained by dividing the length information bya data size transmittable by a symbol of a legacy physical layer frame,wherein the data size transmittable by a symbol of the legacy physicallayer frame is 3 octets when a data rate of the legacy physical layerframe is 6 Mbps, and determining the number of symbols of the data ofthe non-legacy physical layer frame according to a following equation,$N_{SYM} = {\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{{HE}\;\_\;{PREAMBLE}}} \right)/T_{SYM}} \right\rfloor - b_{{PE}\;\_\;{Disambiguity}}}$where [x] denotes a largest integer less than or equal to x, L_LENGTHdenotes the length information, m denotes a value obtained bysubtracting the remaining value from the data size transmittable by asymbol of the legacy physical layer frame, b_(PE) _(_) _(Disambiguity)denotes a value of PE Disambiguity field, T_(HE) _(_) _(PREAMBLE)denotes a duration of non-legacy preamble of the non-legacy physicallayer frame, T_(SYM) denotes a duration of a symbol of the data of thenon-legacy physical layer frame, wherein the PE Disambiguity field isset based on the duration of a symbol of the data of the non-legacyphysical layer frame and an increment of duration to set a value of thelength information based on a duration of a symbol of legacy physicallayer frame.
 9. The method of claim 8, the method further comprisesobtaining a duration of a packet extension which is a padding of thenon-legacy physical layer frame, according to a following equation,$T_{PE} = {\left\lfloor \frac{\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{{HE}\;\_\;{PREAMBLE}}} \right) - {N_{SYM} \times T_{SYM}}}{4} \right\rfloor \times 4}$where [x] denotes a largest integer less than or equal to x, L_LENGTHdenotes the length information, m denotes the value obtained bysubtracting the remaining value from the data size transmittable by asymbol of the legacy physical layer frame, T_(HE) _(_) _(PREAMBLE)denotes the duration of non-legacy preamble of the non-legacy physicallayer frame, T_(SYM) denotes the duration of a symbol of the data of thenon-legacy physical layer frame.
 10. The method of claim 8, wherein theincrement of duration is a value obtained by multiplying a differencebetween a value obtained by performing a ceiling operation on a valueobtained by dividing the duration of the non-legacy physical layer frameafter the legacy signaling field by the duration of a symbol of thelegacy physical layer frame and the value obtained by dividing theduration of the non-legacy physical layer frame after the legacysignaling field by the duration of a symbol of the legacy physical layerframe by the duration of a symbol of the legacy physical layer frame.11. The method of claim 8, the method further comprises determining aformat of a non-legacy signaling field included in the non-legacyphysical layer frame based on the length information.
 12. The method ofclaim 11, wherein determining the format of a non-legacy signaling fieldincluded in the non-legacy physical layer frame comprises determiningwhether the non-legacy physical layer frame comprises a predeterminedsignaling field based on the length information.
 13. The method of claim8, wherein the obtaining the information other than the information onthe duration of the non-legacy physical layer frame comprises obtainingthe information other than the information on the duration of thenon-legacy physical layer frame based on the remaining value and amodulation method of a third symbol after the legacy signaling field.14. The method of claim 13, wherein the modulation method is BinaryPhase Shift Keying (BPSK) or Quadrature Binary Phase Shift Keying(QBPSK).